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/settings_ui/src/extension.dart

@@ -27,7 +27,15 @@ class SettingsUiExtension extends ClideExtension {
   List<ContributionPoint> get contributions => [
     // Opens the Settings panel. Palette + File-menu entry come for free off
     // the title; ctrl+, is the conventional settings shortcut.
-    CommandContribution(id: 'settings.open', command: 'settings.open', title: 'Settings…', defaultBinding: 'ctrl+,', run: _open),
+    CommandContribution(
+      id: 'settings.open',
+      command: 'settings.open',
+      title: 'Settings…',
+      titleKey: 'command.open',
+      i18nNamespace: id,
+      defaultBinding: 'ctrl+,',
+      run: _open,
+    ),
   ];
 
   Future<IpcResponse> _open(List<String> args) async {