refactor: simplify expand chat input to 2-state with optimized button layout

- Remove 3-state logic (normal/50%/80%) - now only normal/expanded
- Remove double-click detection and tooltips for simplicity
- Remove platform-specific behavior (same UX for Electron and web)
- Optimize button layout: reduce from 36px to 28px to fit 3 buttons
- Position expand button above history buttons in vertical stack
- Keep 15-line expanded height (360px, capped to available space)

Per upstream dev feedback to keep it simple with one approach

packages/ui/src/components/expand-button.tsx

@@ -1,109 +1,29 @@
-import { createSignal, Show } from "solid-js"
+import { Show } from "solid-js"
 import { Maximize2, Minimize2 } from "lucide-solid"
-import { isElectronHost } from "../lib/runtime-env"
 
 interface ExpandButtonProps {
-  expandState: () => "normal" | "fifty" | "eighty" | "expanded"
-  onToggleExpand: (nextState: "normal" | "fifty" | "eighty" | "expanded") => void
+  expandState: () => "normal" | "expanded"
+  onToggleExpand: (nextState: "normal" | "expanded") => void
 }
 
 export default function ExpandButton(props: ExpandButtonProps) {
-  const [clickTime, setClickTime] = createSignal<number>(0)
-  const [clickTimer, setClickTimer] = createSignal<number | null>(null)
-  const DOUBLE_CLICK_THRESHOLD = 300
-
-  // Check if we're in Electron (desktop app with 3-state support)
-  const isDesktopApp = isElectronHost()
-
   function handleClick() {
     const current = props.expandState()
-
-    if (!isDesktopApp) {
-      // Web/Mobile: Simple 2-state toggle (instant, no delay)
-      if (current === "normal") {
-        props.onToggleExpand("expanded")
-      } else {
-        props.onToggleExpand("normal")
-      }
-      return
-    }
-
-    // Electron: 3-state with double-click detection
-    const now = Date.now()
-    const lastClick = clickTime()
-    const isDoubleClick = now - lastClick < DOUBLE_CLICK_THRESHOLD
-
-    // Clear any pending single-click timer
-    const timer = clickTimer()
-    if (timer !== null) {
-      clearTimeout(timer)
-      setClickTimer(null)
-    }
-
-    if (isDoubleClick) {
-      // Double click behavior - execute immediately
-      if (current === "normal") {
-        props.onToggleExpand("eighty")
-      } else if (current === "fifty") {
-        props.onToggleExpand("eighty")
-      } else {
-        props.onToggleExpand("fifty")
-      }
-      // Reset click time to prevent triple-click issues
-      setClickTime(0)
-    } else {
-      // Single click behavior - delay to wait for potential double-click
-      setClickTime(now)
-
-      const newTimer = window.setTimeout(() => {
-        const currentState = props.expandState()
-        if (currentState === "normal") {
-          props.onToggleExpand("fifty")
-        } else {
-          props.onToggleExpand("normal")
-        }
-        setClickTimer(null)
-      }, DOUBLE_CLICK_THRESHOLD)
-
-      setClickTimer(newTimer)
-    }
-  }
-
-  const getTooltip = () => {
-    // No tooltip for web/mobile - only Electron gets tooltips
-    if (!isDesktopApp) {
-      return undefined
-    }
-
-    const current = props.expandState()
-    if (current === "normal") {
-      return "Click to expand (50%) • Double-click to expand further (80%)"
-    } else if (current === "fifty") {
-      return "Double-click to expand to 80% • Click to minimize"
-    } else {
-      return "Click to minimize • Double-click to reduce to 50%"
-    }
-  }
-
-  const isExpanded = () => {
-    const state = props.expandState()
-    return state !== "normal"
+    props.onToggleExpand(current === "normal" ? "expanded" : "normal")
   }
 
   return (
     <button
       type="button"
-      class={`prompt-expand-button ${isDesktopApp ? "desktop-mode" : "web-mode"}`}
+      class="prompt-expand-button"
       onClick={handleClick}
-      disabled={false}
       aria-label="Toggle chat input height"
-      data-tooltip={getTooltip()}
     >
       <Show
-        when={!isExpanded()}
-        fallback={<Minimize2 class="h-5 w-5" aria-hidden="true" />}
+        when={props.expandState() === "normal"}
+        fallback={<Minimize2 class="h-4 w-4" aria-hidden="true" />}
       >
-        <Maximize2 class="h-5 w-5" aria-hidden="true" />
+        <Maximize2 class="h-4 w-4" aria-hidden="true" />
       </Show>
     </button>
   )