refactor(i18n): route command + settings manifest labels through the catalog (T-462)

Apply the manifest-i18n foundation across every extension: each
CommandContribution (45, command-palette + menu) gains titleKey + i18nNamespace,
and each SettingsCategory/section/field/option gains its key — with the English
text added to the owning extension's catalog. The settings renderer
(settings_category_view + settings_modal) threads the category's i18nNamespace
down and resolves every label/help/option through it; new catalogs created for
view, cli-install, keybindings-ui. No en_US behaviour change — the command
palette, menus, and settings panel now localize from the catalog (D-21).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/builtin/menubar/src/extension.dart

@@ -30,6 +30,8 @@ class MenuBarExtension extends ClideExtension {
       id: 'file.openFolder',
       command: 'file.openFolder',
       title: 'File: Open Folder…',
+      titleKey: 'command.file.openFolder',
+      i18nNamespace: id,
       run: (_) async {
         await _file.openFolder();
         return IpcResponse.ok(id: '', data: const {});
@@ -39,6 +41,8 @@ class MenuBarExtension extends ClideExtension {
       id: 'file.newWindow',
       command: 'file.newWindow',
       title: 'File: New Window',
+      titleKey: 'command.file.newWindow',
+      i18nNamespace: id,
       run: (_) async {
         _file.newWindow();
         return IpcResponse.ok(id: '', data: const {});
@@ -48,6 +52,8 @@ class MenuBarExtension extends ClideExtension {
       id: 'file.closeWorkspace',
       command: 'file.closeWorkspace',
       title: 'File: Close Project',
+      titleKey: 'command.file.closeWorkspace',
+      i18nNamespace: id,
       run: (_) async {
         _file.closeWorkspace();
         return IpcResponse.ok(id: '', data: const {});
@@ -57,6 +63,8 @@ class MenuBarExtension extends ClideExtension {
       id: 'help.about',
       command: 'help.about',
       title: 'Help: About clide',
+      titleKey: 'command.help.about',
+      i18nNamespace: id,
       run: (_) async {
         services.dialog.show<Object>((ctx, dismiss) => AboutDialog(onDismiss: () => dismiss()));
         return IpcResponse.ok(id: '', data: const {});