feat(palette): unify quick open into command palette with multi-source search

Merge file picker into command palette. Single Cmd+P entry searches
files, sessions, settings pages and commands; groups re-order by best
fuzzy score per source. Sessions show branch labels; git status is
lazily fetched for all session directories on open.

Drop QuickOpenDialog and Cmd+K shortcut.

packages/ui/src/hooks/useKeyboardShortcuts.ts

@@ -18,7 +18,6 @@ export const useKeyboardShortcuts = () => {
   const currentSessionId = useSessionUIStore((s) => s.currentSessionId);
     const abortCurrentOperation = sessionActions.abortCurrentOperation;;
   const toggleCommandPalette = useUIStore((s) => s.toggleCommandPalette);
-  const setQuickOpenOpen = useUIStore((s) => s.setQuickOpenOpen);
   const toggleHelpDialog = useUIStore((s) => s.toggleHelpDialog);
   const toggleSidebar = useUIStore((s) => s.toggleSidebar);
   const toggleRightSidebar = useUIStore((s) => s.toggleRightSidebar);
@@ -62,12 +61,6 @@ export const useKeyboardShortcuts = () => {
         return;
       }
 
-      if (eventMatchesShortcut(e, combo('open_quick_open'))) {
-        e.preventDefault();
-        setQuickOpenOpen(true);
-        return;
-      }
-
       if (eventMatchesShortcut(e, combo('open_status'))) {
         e.preventDefault();
         void showOpenCodeStatus();
@@ -425,7 +418,6 @@ export const useKeyboardShortcuts = () => {
     openNewSessionDraft,
     abortCurrentOperation,
     toggleCommandPalette,
-    setQuickOpenOpen,
     toggleHelpDialog,
     toggleSidebar,
     toggleRightSidebar,

packages/ui/src/hooks/useMenuActions.ts

@@ -90,7 +90,7 @@ export const useMenuActions = (
 ) => {
   const openNewSessionDraft = useSessionUIStore((s) => s.openNewSessionDraft);
   const toggleCommandPalette = useUIStore((s) => s.toggleCommandPalette);
-  const setQuickOpenOpen = useUIStore((s) => s.setQuickOpenOpen);
+  const setCommandPaletteOpen = useUIStore((s) => s.setCommandPaletteOpen);
   const toggleHelpDialog = useUIStore((s) => s.toggleHelpDialog);
   const toggleSidebar = useUIStore((s) => s.toggleSidebar);
   const setSessionSwitcherOpen = useUIStore((s) => s.setSessionSwitcherOpen);
@@ -146,7 +146,7 @@ export const useMenuActions = (
           break;
 
         case 'quick-open':
-          setQuickOpenOpen(true);
+          setCommandPaletteOpen(true);
           break;
 
         case 'new-session':
@@ -237,7 +237,7 @@ export const useMenuActions = (
       setAboutDialogOpen,
       setActiveMainTab,
       setSessionSwitcherOpen,
-      setQuickOpenOpen,
+      setCommandPaletteOpen,
       setSettingsDialogOpen,
       setThemeMode,
       toggleCommandPalette,