feat(i18n): i18n key fields on command + settings contributions (T-462)

Lets manifest labels (command-palette/menu titles, settings labels) localize,
not just displayed widget strings. Adds optional titleKey/i18nNamespace to
CommandContribution and labelKey/helpKey/titleKey + a category i18nNamespace to
the settings schema. The command palette and menu bar now resolve titles via a
shared localizedCommandTitle helper — and the palette's fuzzy search matches
the localized title too (PaletteController.titleResolver). No behaviour change
until the per-extension keys + catalog entries land (placeholder == English).

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

lib/widgets/src/clide_palette.dart

@@ -1,9 +1,22 @@
+import 'package:clide/extension/src/contribution.dart' show CommandContribution;
 import 'package:clide/kernel/kernel.dart';
 import 'package:clide/widgets/src/clide_settings.dart';
 import 'package:clide/widgets/src/clide_text.dart';
 import 'package:clide/widgets/src/typography.dart';
 import 'package:flutter/widgets.dart';
 
+/// The localized display title for a command (T-462): resolves [titleKey] in
+/// [i18nNamespace] when both are set, else the English title (then id). Shared
+/// by the command palette and the menu bar so both localize identically.
+String localizedCommandTitle(BuildContext context, CommandContribution cmd) {
+  final k = cmd.titleKey;
+  final ns = cmd.i18nNamespace;
+  if (k != null && ns != null) {
+    return ClideSettings.i18n.string(context, k, namespace: ns, placeholder: cmd.title ?? cmd.command);
+  }
+  return cmd.title ?? cmd.command;
+}
+
 class ClidePalette extends StatefulWidget {
   const ClidePalette({super.key});
 
@@ -109,6 +122,8 @@ class _ClidePaletteState extends State<ClidePalette> {
       listenable: kernel.palette,
       builder: (ctx, _) {
         if (!kernel.palette.isOpen) return const SizedBox.shrink();
+        // Localize titles for both the fuzzy filter and the rendered rows (T-462).
+        kernel.palette.titleResolver = (cmd) => localizedCommandTitle(ctx, cmd);
         final filtered = kernel.palette.filtered();
         final selected = kernel.palette.selectedIndex;
         return Positioned(
@@ -164,7 +179,7 @@ class _ClidePaletteState extends State<ClidePalette> {
                           final key = _itemKeys.putIfAbsent(i, () => GlobalKey());
                           return _PaletteItem(
                             key: key,
-                            title: cmd.title ?? cmd.command,
+                            title: localizedCommandTitle(ctx, cmd),
                             command: cmd.command,
                             binding: cmd.defaultBinding,
                             highlighted: i == selected,