fix(dashboard): lazy-init useMobileKeyboard so remount has no stale render

When ChatView remounted (e.g. tab switch with keyboard still up), the
hook started with keyboardOpen=false and corrected itself only after
the effect ran. That single stale-state render briefly unhid the
executor status bar, which appeared as a blank pane covering half the
input box before the next state update settled it.

useState initializers now call getKeyboardMetrics() lazily on first
render so the very first paint already reflects the live keyboard
state.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/hooks/useMobileKeyboard.ts

@@ -110,10 +110,23 @@ interface UseMobileKeyboardOptions {
 export function useMobileKeyboard(
   { enabled = true }: UseMobileKeyboardOptions = {},
 ): { keyboardOverlap: number; viewportHeight: number | null; viewportOffsetTop: number; keyboardOpen: boolean } {
-  const [keyboardOverlap, setKeyboardOverlap] = useState(0);
-  const [viewportHeight, setViewportHeight] = useState<number | null>(null);
-  const [viewportOffsetTop, setViewportOffsetTop] = useState(0);
-  const [keyboardOpen, setKeyboardOpen] = useState(false);
+  // Lazy initial values: read the actual visualViewport on first render
+  // so a remount (e.g. switching tabs back with the keyboard up) doesn't
+  // start with keyboardOpen=false. That stale-state render briefly hid
+  // the .chat-thread compensation and unhid the executor status bar,
+  // which then reappeared as a blank pane covering half the composer
+  // before settling.
+  const initialMetrics = (): KeyboardMetrics => {
+    if (!enabled || typeof window === "undefined" || !isMobileDevice()) {
+      return { overlap: 0, open: false, vvHeight: null, vvOffsetTop: 0 };
+    }
+    return getKeyboardMetrics();
+  };
+  const [initial] = useState(initialMetrics);
+  const [keyboardOverlap, setKeyboardOverlap] = useState(initial.overlap);
+  const [viewportHeight, setViewportHeight] = useState<number | null>(initial.vvHeight);
+  const [viewportOffsetTop, setViewportOffsetTop] = useState(initial.vvOffsetTop);
+  const [keyboardOpen, setKeyboardOpen] = useState(initial.open);
 
   useEffect(() => {
     if (!enabled || !isMobileDevice()) {