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/App.tsx

@@ -54,7 +54,6 @@ import { useGitHubAuthStore } from '@/stores/useGitHubAuthStore';
 import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 import type { RuntimeAPIs } from '@/lib/api/types';
 import { TooltipProvider } from '@/components/ui/tooltip';
-import { QuickOpenDialog } from '@/components/ui/QuickOpenDialog';
 import { McpOAuthCallbackPage } from '@/components/sections/mcp/McpOAuthCallbackPage';
 import { MCP_OAUTH_CALLBACK_PATH } from '@/components/sections/mcp/mcpOAuth';
 import { lazyWithChunkRecovery } from '@/lib/chunkLoadRecovery';
@@ -925,7 +924,6 @@ function App({ apis }: AppProps) {
                   {!isBootShell && (
                     <>
                       <ConfigUpdateOverlay />
-                      <QuickOpenDialog />
                       <AboutDialogWrapper />
                       {showMemoryDebug && (
                         <MemoryDebugPanel onClose={() => setShowMemoryDebug(false)} />