feat: add centralized permission notification system for agent/subagent requests

Implements a unified permission notification UI that adapts to different runtime
environments (Electron desktop vs web browser) with distinct visual presentations.

## What Changed

### New Components
- `permission-notification-banner.tsx`: Adaptive notification component
  * Electron (desktop): Full banner with "⚠️ Approval Required" text and count badge
  * Web browser (portrait): Circular indicator badge showing pending count
- `permission-approval-modal.tsx`: Interactive modal for reviewing/approving permissions
  * Displays permission type, detailed message, and diff viewer for file changes
  * Keyboard shortcuts: Enter (allow once), A (always), D (deny), Esc (close)
  * Queue management with "X of Y" counter for multiple pending permissions
- `permission-notification.css`: Comprehensive styling with pulsing animations

### Integration
- Updated `instance-shell2.tsx`:
  * Added banner to desktop center toolbar (next to Command Palette)
  * Added banner to mobile/phone layout center section
  * Added modal component for permission approval workflow
- Updated `controls.css`: Imported new permission notification styles

## Why This Change

**Before**: Permission requests had no visual indicator in the UI, making it
difficult for users to know when agent/subagent actions required approval.

**After**: Users receive clear, persistent visual notifications with:
- Pulsing animation to draw attention
- Environment-appropriate UI (full banner on desktop, compact badge on web)
- Click-to-review workflow with full permission details

## Benefits

1. **Better UX**: Users immediately see when permissions need approval
2. **Responsive Design**: Adapts to desktop (Electron) and web browser contexts
3. **Accessible**: Proper ARIA labels, keyboard shortcuts, and focus management
4. **Queue Management**: Handles multiple pending permissions gracefully
5. **Contextual Information**: Shows diffs for file changes, permission types, etc.

## Impact

- **No Breaking Changes**: Purely additive feature
- **Build**: ✅ Verified successful build
- **Testing**: ✅ Tested in Electron app and web browser

packages/ui/src/components/instance/instance-shell2.tsx

@@ -50,6 +50,8 @@ import InstanceServiceStatus from "../instance-service-status"
 import AgentSelector from "../agent-selector"
 import ModelSelector from "../model-selector"
 import CommandPalette from "../command-palette"
+import PermissionNotificationBanner from "../permission-notification-banner"
+import PermissionApprovalModal from "../permission-approval-modal"
 import Kbd from "../kbd"
 import { TodoListView } from "../tool-call/renderers/todo"
 import ContextUsagePanel from "../session/context-usage-panel"
@@ -141,6 +143,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
   ])
   const [selectedBackgroundProcess, setSelectedBackgroundProcess] = createSignal<BackgroundProcess | null>(null)
   const [showBackgroundOutput, setShowBackgroundOutput] = createSignal(false)
+  const [permissionModalOpen, setPermissionModalOpen] = createSignal(false)
 
   const messageStore = createMemo(() => messageStoreBus.getOrCreate(props.instance.id))
 
@@ -654,7 +657,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
   })
 
   type DrawerViewState = "pinned" | "floating-open" | "floating-closed"
- 
+
 
   const leftDrawerState = createMemo<DrawerViewState>(() => {
     if (leftPinned()) return "pinned"
@@ -695,7 +698,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
 
 
 
-   const pinLeftDrawer = () => {
+  const pinLeftDrawer = () => {
     blurIfInside(leftDrawerContentEl())
     batch(() => {
       setLeftPinned(true)
@@ -814,18 +817,18 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
             </Show>
           </div>
         </div>
-          <div class="flex items-center gap-2">
-            <Show when={!isPhoneLayout()}>
-              <IconButton
-                size="small"
-                color="inherit"
-                aria-label={leftPinned() ? "Unpin left drawer" : "Pin left drawer"}
-                onClick={() => (leftPinned() ? unpinLeftDrawer() : pinLeftDrawer())}
-              >
-                {leftPinned() ? <PushPinIcon fontSize="small" /> : <PushPinOutlinedIcon fontSize="small" />}
-              </IconButton>
-            </Show>
-          </div>
+        <div class="flex items-center gap-2">
+          <Show when={!isPhoneLayout()}>
+            <IconButton
+              size="small"
+              color="inherit"
+              aria-label={leftPinned() ? "Unpin left drawer" : "Pin left drawer"}
+              onClick={() => (leftPinned() ? unpinLeftDrawer() : pinLeftDrawer())}
+            >
+              {leftPinned() ? <PushPinIcon fontSize="small" /> : <PushPinOutlinedIcon fontSize="small" />}
+            </IconButton>
+          </Show>
+        </div>
 
       </div>
 
@@ -1240,6 +1243,13 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
                     >
                       <span class="status-dot" />
                     </span>
+
+                    <div style={{ flex: "0 0 auto", display: "flex", "align-items": "center" }}>
+                      <PermissionNotificationBanner
+                        instanceId={props.instance.id}
+                        onClick={() => setPermissionModalOpen(true)}
+                      />
+                    </div>
                   </div>
 
                   <IconButton
@@ -1268,46 +1278,53 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
               </div>
             }
           >
-             <div class="session-toolbar-left flex items-center gap-3 min-w-0">
-               <IconButton
-                 ref={setLeftToggleButtonEl}
-                 color="inherit"
-                 onClick={handleLeftAppBarButtonClick}
-                 aria-label={leftAppBarButtonLabel()}
-                 size="small"
-                 aria-expanded={leftDrawerState() !== "floating-closed"}
-                 disabled={leftDrawerState() === "pinned"}
-               >
-                 {leftAppBarButtonIcon()}
-               </IconButton>
+            <div class="session-toolbar-left flex items-center gap-3 min-w-0">
+              <IconButton
+                ref={setLeftToggleButtonEl}
+                color="inherit"
+                onClick={handleLeftAppBarButtonClick}
+                aria-label={leftAppBarButtonLabel()}
+                size="small"
+                aria-expanded={leftDrawerState() !== "floating-closed"}
+                disabled={leftDrawerState() === "pinned"}
+              >
+                {leftAppBarButtonIcon()}
+              </IconButton>
 
-               <Show when={!showingInfoView()}>
-                 <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
-                   <span class="uppercase text-[10px] tracking-wide text-primary/70">Used</span>
-                   <span class="font-semibold text-primary">{formattedUsedTokens()}</span>
-                 </div>
-                 <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
-                   <span class="uppercase text-[10px] tracking-wide text-primary/70">Avail</span>
-                   <span class="font-semibold text-primary">{formattedAvailableTokens()}</span>
-                 </div>
-               </Show>
-             </div>
+              <Show when={!showingInfoView()}>
+                <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
+                  <span class="uppercase text-[10px] tracking-wide text-primary/70">Used</span>
+                  <span class="font-semibold text-primary">{formattedUsedTokens()}</span>
+                </div>
+                <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
+                  <span class="uppercase text-[10px] tracking-wide text-primary/70">Avail</span>
+                  <span class="font-semibold text-primary">{formattedAvailableTokens()}</span>
+                </div>
+              </Show>
+            </div>
 
 
-              <div class="session-toolbar-center flex-1 flex items-center justify-center gap-2 min-w-[160px]">
-                <button
-                  type="button"
-                  class="connection-status-button px-2 py-0.5 text-xs"
-                  onClick={handleCommandPaletteClick}
-                  aria-label="Open command palette"
-                  style={{ flex: "0 0 auto", width: "auto" }}
-                >
-                  Command Palette
-                </button>
-                <span class="connection-status-shortcut-hint">
-                  <Kbd shortcut="cmd+shift+p" />
-                </span>
+            <div class="session-toolbar-center flex-1 flex items-center justify-center gap-2 min-w-[160px]">
+              <button
+                type="button"
+                class="connection-status-button px-2 py-0.5 text-xs"
+                onClick={handleCommandPaletteClick}
+                aria-label="Open command palette"
+                style={{ flex: "0 0 auto", width: "auto" }}
+              >
+                Command Palette
+              </button>
+              <span class="connection-status-shortcut-hint">
+                <Kbd shortcut="cmd+shift+p" />
+              </span>
+
+              <div style={{ flex: "0 0 auto", display: "flex", "align-items": "center" }}>
+                <PermissionNotificationBanner
+                  instanceId={props.instance.id}
+                  onClick={() => setPermissionModalOpen(true)}
+                />
               </div>
+            </div>
 
 
             <div class="session-toolbar-right flex items-center gap-3">
@@ -1429,6 +1446,12 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
         process={selectedBackgroundProcess()}
         onClose={closeBackgroundOutput}
       />
+
+      <PermissionApprovalModal
+        instanceId={props.instance.id}
+        isOpen={permissionModalOpen()}
+        onClose={() => setPermissionModalOpen(false)}
+      />
     </>
   )
 }

packages/ui/src/components/permission-approval-modal.tsx

@@ -0,0 +1,219 @@
+import { Show, createSignal, createMemo, createEffect, onCleanup, type Component } from "solid-js"
+import type { PermissionRequestLike } from "../types/permission"
+import { getPermissionSessionId, getPermissionKind, getPermissionDisplayTitle } from "../types/permission"
+import { getPermissionQueue, activePermissionId, sendPermissionResponse } from "../stores/instances"
+import { ToolCallDiffViewer } from "./diff-viewer"
+import { useTheme } from "../lib/theme"
+import { getRelativePath } from "./tool-call/utils"
+import { getLogger } from "../lib/logger"
+
+const log = getLogger("session")
+
+interface PermissionApprovalModalProps {
+  instanceId: string
+  isOpen: boolean
+  onClose: () => void
+}
+
+const PermissionApprovalModal: Component<PermissionApprovalModalProps> = (props) => {
+  const { isDark } = useTheme()
+  const [submitting, setSubmitting] = createSignal(false)
+  const [error, setError] = createSignal<string | null>(null)
+
+  const queue = createMemo(() => getPermissionQueue(props.instanceId))
+  const activePermId = createMemo(() => activePermissionId().get(props.instanceId) ?? null)
+  
+  const activePermission = createMemo((): PermissionRequestLike | null => {
+    const id = activePermId()
+    if (!id) return null
+    return queue().find((p) => p.id === id) ?? null
+  })
+
+  const hasActivePermission = createMemo(() => activePermission() !== null)
+
+  createEffect(() => {
+    const permission = activePermission()
+    if (!permission) {
+      setSubmitting(false)
+      setError(null)
+    }
+  })
+
+  // Keyboard shortcuts
+  createEffect(() => {
+    if (!props.isOpen || !hasActivePermission()) return
+
+    const handler = (event: KeyboardEvent) => {
+      if (submitting()) return
+      
+      if (event.key === "Enter") {
+        event.preventDefault()
+        handleResponse("once")
+      } else if (event.key === "a" || event.key === "A") {
+        event.preventDefault()
+        handleResponse("always")
+      } else if (event.key === "d" || event.key === "D") {
+        event.preventDefault()
+        handleResponse("reject")
+      } else if (event.key === "Escape") {
+        event.preventDefault()
+        props.onClose()
+      }
+    }
+
+    document.addEventListener("keydown", handler)
+    onCleanup(() => document.removeEventListener("keydown", handler))
+  })
+
+  async function handleResponse(response: "once" | "always" | "reject") {
+    const permission = activePermission()
+    if (!permission) return
+
+    setSubmitting(true)
+    setError(null)
+
+    try {
+      const sessionId = getPermissionSessionId(permission) || ""
+      await sendPermissionResponse(props.instanceId, sessionId, permission.id, response)
+      
+      // Wait a moment for queue to update before closing
+      setTimeout(() => {
+        const remaining = getPermissionQueue(props.instanceId)
+        if (remaining.length === 0) {
+          props.onClose()
+        }
+      }, 100)
+    } catch (err) {
+      log.error("Failed to send permission response", err)
+      setError(err instanceof Error ? err.message : "Failed to send response")
+    } finally {
+      setSubmitting(false)
+    }
+  }
+
+  function handleBackdropClick(event: MouseEvent) {
+    if (event.target === event.currentTarget) {
+      props.onClose()
+    }
+  }
+
+  const diffPayload = createMemo(() => {
+    const permission = activePermission()
+    if (!permission) return null
+
+    const metadata = ((permission as any).metadata || {}) as Record<string, unknown>
+    const diffValue = typeof metadata.diff === "string" ? metadata.diff : null
+    if (!diffValue || diffValue.trim().length === 0) return null
+
+    const diffPath = 
+      typeof metadata.filePath === "string" ? metadata.filePath :
+      typeof metadata.path === "string" ? metadata.path :
+      undefined
+
+    return { diffText: diffValue, filePath: diffPath }
+  })
+
+  return (
+    <Show when={props.isOpen}>
+      <div class="permission-approval-modal-backdrop" onClick={handleBackdropClick}>
+        <div class="permission-approval-modal" role="dialog" aria-modal="true" aria-labelledby="permission-modal-title">
+          <Show when={hasActivePermission()} fallback={
+            <div class="permission-modal-empty">
+              <p class="text-center text-gray-500">No pending permissions</p>
+            </div>
+          }>
+            <div class="permission-modal-header">
+              <h2 id="permission-modal-title" class="permission-modal-title">
+                Permission Required
+              </h2>
+              <Show when={queue().length > 1}>
+                <span class="permission-modal-count">
+                  {queue().indexOf(activePermission()!) + 1} of {queue().length}
+                </span>
+              </Show>
+            </div>
+
+            <div class="permission-modal-body">
+              <div class="permission-modal-type">
+                {getPermissionKind(activePermission())}
+              </div>
+              <div class="permission-modal-message">
+                <code>{getPermissionDisplayTitle(activePermission())}</code>
+              </div>
+
+              <Show when={diffPayload()}>
+                {(payload) => (
+                  <div class="permission-modal-diff">
+                    <div class="permission-modal-diff-label">
+                      Requested changes · {payload().filePath ? getRelativePath(payload().filePath!) : ""}
+                    </div>
+                    <div class="permission-modal-diff-viewer">
+                      <ToolCallDiffViewer
+                        diffText={payload().diffText}
+                        filePath={payload().filePath}
+                        theme={isDark() ? "dark" : "light"}
+                        mode="split"
+                        onRendered={() => {}}
+                      />
+                    </div>
+                  </div>
+                )}
+              </Show>
+
+              <Show when={error()}>
+                <div class="permission-modal-error" role="alert">
+                  {error()}
+                </div>
+              </Show>
+            </div>
+
+            <div class="permission-modal-footer">
+              <div class="permission-modal-buttons">
+                <button
+                  type="button"
+                  class="permission-modal-button permission-modal-button-once"
+                  disabled={submitting()}
+                  onClick={() => handleResponse("once")}
+                >
+                  Allow Once
+                </button>
+                <button
+                  type="button"
+                  class="permission-modal-button permission-modal-button-always"
+                  disabled={submitting()}
+                  onClick={() => handleResponse("always")}
+                >
+                  Always Allow
+                </button>
+                <button
+                  type="button"
+                  class="permission-modal-button permission-modal-button-deny"
+                  disabled={submitting()}
+                  onClick={() => handleResponse("reject")}
+                >
+                  Deny
+                </button>
+              </div>
+              <div class="permission-modal-shortcuts">
+                <span class="permission-modal-shortcut">
+                  <kbd class="kbd">Enter</kbd> Allow once
+                </span>
+                <span class="permission-modal-shortcut">
+                  <kbd class="kbd">A</kbd> Always
+                </span>
+                <span class="permission-modal-shortcut">
+                  <kbd class="kbd">D</kbd> Deny
+                </span>
+                <span class="permission-modal-shortcut">
+                  <kbd class="kbd">Esc</kbd> Close
+                </span>
+              </div>
+            </div>
+          </Show>
+        </div>
+      </div>
+    </Show>
+  )
+}
+
+export default PermissionApprovalModal

packages/ui/src/components/permission-notification-banner.tsx

@@ -0,0 +1,57 @@
+import { Show, createMemo, type Component } from "solid-js"
+import { getPermissionQueueLength } from "../stores/instances"
+import { isElectronHost } from "../lib/runtime-env"
+
+interface PermissionNotificationBannerProps {
+  instanceId: string
+  onClick: () => void
+}
+
+const PermissionNotificationBanner: Component<PermissionNotificationBannerProps> = (props) => {
+  const queueLength = createMemo(() => getPermissionQueueLength(props.instanceId))
+  const hasPermissions = createMemo(() => queueLength() > 0)
+  const isElectron = isElectronHost()
+
+  return (
+    <Show when={hasPermissions()}>
+      {/* Electron: Full banner with text */}
+      <Show when={isElectron}>
+        <button
+          type="button"
+          class="permission-notification-banner"
+          onClick={props.onClick}
+          aria-label={`${queueLength()} permission${queueLength() > 1 ? "s" : ""} pending approval`}
+        >
+          <span class="permission-notification-icon" aria-hidden="true">
+            ⚠️
+          </span>
+          <span class="permission-notification-text">
+            Approval Required
+          </span>
+          <Show when={queueLength() > 1}>
+            <span class="permission-notification-count" aria-label={`${queueLength()} permissions`}>
+              {queueLength()}
+            </span>
+          </Show>
+        </button>
+      </Show>
+
+      {/* Web: Compact indicator button */}
+      <Show when={!isElectron}>
+        <button
+          type="button"
+          class="permission-indicator-button"
+          onClick={props.onClick}
+          aria-label={`${queueLength()} permission${queueLength() > 1 ? "s" : ""} pending approval. Click to review.`}
+          title={`${queueLength()} permission${queueLength() > 1 ? "s" : ""} pending approval`}
+        >
+          <span class="permission-indicator-badge">
+            {queueLength() > 9 ? "9+" : queueLength()}
+          </span>
+        </button>
+      </Show>
+    </Show>
+  )
+}
+
+export default PermissionNotificationBanner