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/cli_install/src/extension.dart

@@ -65,6 +65,8 @@ class CliInstallExtension extends ClideExtension {
       id: 'clide.installCli',
       command: 'clide.installCli',
       title: "clide: Install 'clide' command in PATH",
+      titleKey: 'command.clide.installCli',
+      i18nNamespace: id,
       run: (_) async {
         final r = _resolved.install();
         final ctx = _ctx;