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>

src/i18n/locales/de/chat.json

@@ -188,7 +188,8 @@
       "codex": "Bereit, Codex mit {{model}} zu verwenden. Gib unten deine Nachricht ein.",
       "gemini": "Bereit, Gemini mit {{model}} zu verwenden. Gib unten deine Nachricht ein.",
       "default": "Wähl oben einen Anbieter, um zu beginnen"
-    }
+    },
+    "pressToSearch": "Drücke <kbd>{{shortcut}}</kbd>, um Sitzungen, Dateien und Commits zu durchsuchen"
   },
   "session": {
     "continue": {