Create command palette and add new features for search and actions (#728)

* refactor(ui): replace in-repo Command primitive with cmdk wrapper

* feat(command-palette): add global Cmd+K palette with v1 actions

* feat(command-palette): add session, file, and commit search sources

* refactor: add provider names to model constants

* feat(command-palette): add settings, navigation, message search, and ⌘K hints

* feat(command-palette): add git fetch/pull/push and branch switch actions

* refactor(command-palette): consolidate fetch source hooks behind useApiSource

* refactor(command-palette): extract useCommandKey and SETTINGS_MAIN_TABS metadata

* refactor(command-palette): extract groups into declarative registry

* refactor(command-palette): wire openFile through PaletteOpsContext

* refactor: migrate openSettings and refreshProjects from window.* to PaletteOpsContext

* refactor(command-palette): inline groups and delete registry indirection

* refactor(command-palette): return items array directly from source hooks

* refactor(palette-ops): flatten Handle wrapper into ref-based registry

* refactor: inline useCommandKey as MOD_KEY constant in two call sites

* feat: introduce pages and fix bug on branch switching

* fix: small labels

* fix: coderabbit issues

* fix: coderabbit comments

* Update src/components/chat/view/subcomponents/ProviderSelectionEmptyState.tsx

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

package.json

@@ -91,6 +91,7 @@
     "chokidar": "^4.0.3",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "cmdk": "^1.1.1",
     "cors": "^2.8.5",
     "cross-spawn": "^7.0.3",
     "express": "^4.18.2",