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/lib/shortcuts.ts

@@ -104,13 +104,6 @@ export function keyToShortcutToken(key: string): string {
 }
 
 const SHORTCUT_ACTIONS: ReadonlyArray<ShortcutAction> = [
-  {
-    id: 'open_quick_open',
-    defaultCombo: 'mod+p',
-    label: 'Open quick open',
-    description: 'Open the quick open dialog',
-    customizable: true,
-  },
   {
     id: 'open_go_to_line',
     defaultCombo: 'alt+g',
@@ -120,7 +113,7 @@ const SHORTCUT_ACTIONS: ReadonlyArray<ShortcutAction> = [
   },
   {
     id: 'open_command_palette',
-    defaultCombo: 'mod+k',
+    defaultCombo: 'mod+p',
     label: 'Open command palette',
     description: 'Open the command palette',
     customizable: true,