fix: keep Windows header menu aligned

Moved the Windows app menu into the fixed titlebar controls
Kept sidebar controls stable when opening and closing the sidebar
Documented longer validation timeouts for workspace checks

packages/ui/src/components/layout/TitlebarLeftControls.tsx

@@ -7,6 +7,7 @@ import { useI18n } from '@/lib/i18n';
 import { useProjectActionsContext } from '@/hooks/useProjectActionsContext';
 import { ProjectActionsButton } from '@/components/layout/ProjectActionsButton';
 import { formatShortcutForDisplay, getEffectiveShortcutCombo } from '@/lib/shortcuts';
+import { invokeDesktop } from '@/lib/desktop';
 
 const ICON_BUTTON_CLASS =
   'app-region-no-drag inline-flex h-8 w-8 items-center justify-center gap-2 rounded-md typography-ui-label font-medium text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary hover:bg-interactive-hover transition-colors';
@@ -31,6 +32,22 @@ export const TitlebarLeftControls: React.FC = () => {
   const clusterRef = React.useRef<HTMLDivElement | null>(null);
 
   const toggleShortcut = formatShortcutForDisplay(getEffectiveShortcutCombo('toggle_sidebar', shortcutOverrides));
+  const isWindowsElectronDesktop = React.useMemo(() => {
+    if (typeof window === 'undefined') {
+      return false;
+    }
+    return Boolean(window.__OPENCHAMBER_ELECTRON__) && window.__OPENCHAMBER_PLATFORM__ === 'win32';
+  }, []);
+
+  const handleOpenWindowsAppMenu = React.useCallback((event: React.MouseEvent<HTMLButtonElement>) => {
+    const rect = event.currentTarget.getBoundingClientRect();
+    void invokeDesktop('desktop_show_app_menu', {
+      x: rect.left,
+      y: rect.bottom,
+    }).catch((error) => {
+      console.warn('[titlebar] failed to open app menu', error);
+    });
+  }, []);
 
   React.useEffect(() => {
     if (typeof document === 'undefined') {
@@ -71,6 +88,24 @@ export const TitlebarLeftControls: React.FC = () => {
       }}
     >
       <div ref={clusterRef} className="flex items-center gap-2">
+        {isWindowsElectronDesktop ? (
+          <Tooltip>
+            <TooltipTrigger asChild>
+              <button
+                type="button"
+                onClick={handleOpenWindowsAppMenu}
+                aria-label={t('header.actions.openAppMenuAria')}
+                className={cn(ICON_BUTTON_CLASS, 'shrink-0')}
+              >
+                <Icon name="menu-2" className="h-[18px] w-[18px]" />
+              </button>
+            </TooltipTrigger>
+            <TooltipContent>
+              <p>{t('header.actions.openAppMenu')}</p>
+            </TooltipContent>
+          </Tooltip>
+        ) : null}
+
         <Tooltip>
           <TooltipTrigger asChild>
             <button