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/theme_picker/src/extension.dart

@@ -28,7 +28,15 @@ class ThemePickerExtension extends ClideExtension {
     // "Theme…" to disambiguate from the schema-driven Settings panel's
     // `settings.open` (T-444); the theme picker folds into that panel's
     // Appearance category in T-452.
-    CommandContribution(id: 'theme.pick', command: 'theme.pick', title: 'Theme…', defaultBinding: 'ctrl+k', run: _pick),
+    CommandContribution(
+      id: 'theme.pick',
+      command: 'theme.pick',
+      title: 'Theme…',
+      titleKey: 'command.pick',
+      i18nNamespace: id,
+      defaultBinding: 'ctrl+k',
+      run: _pick,
+    ),
     // Always-visible switcher in the far-right status bar (T-234).
     // priority >= 100 places it in the right group; registered after
     // ipc-status so it sits to its right.
@@ -36,49 +44,59 @@ class ThemePickerExtension extends ClideExtension {
     // Appearance settings category (T-452) — the theme picker as the schema
     // engine's one custom control, registered against the control registry.
     SettingsControlContribution(id: 'theme-picker.appearance-control', customId: 'theme.picker', builder: (_) => const AppearanceThemeControl()),
-    const SettingsCategoryContribution(
+    SettingsCategoryContribution(
       id: 'appearance',
       category: SettingsCategory(
         id: 'appearance',
         title: 'Appearance',
+        titleKey: 'settings.appearance.title',
+        i18nNamespace: id,
         iconName: 'palette',
         priority: 10,
         sections: [
           SettingsSection(
             label: 'Theme',
+            labelKey: 'settings.appearance.section.theme',
             fields: [
               SettingsField(
                 key: 'app.theme',
                 kind: SettingsFieldKind.custom,
                 label: 'Theme',
+                labelKey: 'settings.appearance.field.theme.label',
                 help: 'Color theme; high contrast switches to the accessible variant.',
+                helpKey: 'settings.appearance.field.theme.help',
                 customId: 'theme.picker',
               ),
             ],
           ),
           SettingsSection(
             label: 'Typography',
+            labelKey: 'settings.appearance.section.typography',
             fields: [
               SettingsField(
                 key: kUiFontSettingKey,
                 kind: SettingsFieldKind.select,
                 label: 'UI font',
+                labelKey: 'settings.appearance.field.uiFont.label',
                 help: 'Typeface for the app interface; applies live.',
+                helpKey: 'settings.appearance.field.uiFont.help',
                 defaultValue: 'JosefinSans',
                 options: [
-                  SettingsOption(value: 'JosefinSans', label: 'Josefin Sans'),
-                  SettingsOption(value: 'Inter', label: 'Inter'),
+                  SettingsOption(value: 'JosefinSans', label: 'Josefin Sans', labelKey: 'settings.appearance.field.uiFont.option.josefinSans'),
+                  SettingsOption(value: 'Inter', label: 'Inter', labelKey: 'settings.appearance.field.uiFont.option.inter'),
                 ],
               ),
               SettingsField(
                 key: kMonoFontSettingKey,
                 kind: SettingsFieldKind.select,
                 label: 'Monospace font',
+                labelKey: 'settings.appearance.field.monoFont.label',
                 help: 'Terminal, diffs, code, and IDs; applies live.',
+                helpKey: 'settings.appearance.field.monoFont.help',
                 defaultValue: 'JetBrainsMono',
                 options: [
-                  SettingsOption(value: 'JetBrainsMono', label: 'JetBrains Mono'),
-                  SettingsOption(value: 'FiraMono', label: 'Fira Mono'),
+                  SettingsOption(value: 'JetBrainsMono', label: 'JetBrains Mono', labelKey: 'settings.appearance.field.monoFont.option.jetBrainsMono'),
+                  SettingsOption(value: 'FiraMono', label: 'Fira Mono', labelKey: 'settings.appearance.field.monoFont.option.firaMono'),
                 ],
               ),
             ],