fix(ui): focus prompt on session activate

packages/ui/src/components/session/session-view.tsx

@@ -1,4 +1,4 @@
-import { Show, For, createMemo, createEffect, type Component } from "solid-js"
+import { Show, For, createMemo, createEffect, on, type Component } from "solid-js"
 import { Expand } from "lucide-solid"
 import type { Session } from "../../types/session"
 import type { Attachment } from "../../types/attachment"
@@ -112,6 +112,43 @@ export const SessionView: Component<SessionViewProps> = (props) => {
     if (!props.isActive) return
     scheduleScrollToBottom()
   })
+
+  createEffect(
+    on(
+      () => props.isActive,
+      (isActive) => {
+        if (!isActive) return
+
+        // Don't steal focus from other inputs (command palette, dialogs, selectors, etc.)
+        if (typeof document === "undefined") return
+        const activeEl = document.activeElement as HTMLElement | null
+        const activeIsInput =
+          activeEl?.tagName === "INPUT" ||
+          activeEl?.tagName === "TEXTAREA" ||
+          activeEl?.tagName === "SELECT" ||
+          Boolean(activeEl?.isContentEditable)
+        if (activeIsInput) return
+
+        const modalOpen = Boolean(document.querySelector('[role="dialog"][aria-modal="true"]'))
+        if (modalOpen) return
+
+        // Defer until the session pane is visible and the textarea is mounted.
+        requestAnimationFrame(() => {
+          requestAnimationFrame(() => {
+            const textarea = rootRef?.querySelector<HTMLTextAreaElement>(".prompt-input")
+            if (!textarea) return
+            if (textarea.disabled) return
+
+            try {
+              textarea.focus({ preventScroll: true } as any)
+            } catch {
+              textarea.focus()
+            }
+          })
+        })
+      },
+    ),
+  )
   let quoteHandler: ((text: string, mode: "quote" | "code") => void) | null = null
  
   createEffect(() => {