refactor(i18n): route claude pane labels through the catalog (T-464)

Migrate the hardcoded user-facing strings across builtin.claude — composer,
conversation cards/segments, permission + AskUserQuestion prompts, task dock,
meta-sidebar (activity/config/team/roster), session/model pickers — to
ClideSettings.i18n.string/.interpolated, English kept as the placeholder;
builtin.claude_en_us.json extended to cover them. Context threaded into the
context-free render helpers (toolInputBody chain, _ConversationTurn) the same
way the mono family already is. No en_US behaviour change (D-21).

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

lib/builtin/claude/src/image_thumbnail.dart

@@ -49,7 +49,13 @@ class ImageThumbnail extends StatelessWidget {
     final t = ClideSettings.theme.of(context).surface;
     return Semantics(
       button: true,
-      label: 'Image $_fileName',
+      label: ClideSettings.i18n.interpolated(
+        context,
+        'image.semantics',
+        namespace: 'builtin.claude',
+        placeholder: 'Image $_fileName',
+        replacers: [I18nReplacer(from: '{name}', replace: _fileName)],
+      ),
       excludeSemantics: true,
       child: ClideTappable(
         onTap: () => openImageLightbox(context, path),