tint the Claude sidebar tab icon with the Claude accent (T-418)

TabContribution gains an optional iconColor honoured by the icon rail:
full-strength when active/hovered, dimmed (70%) when idle, so the tint
reads as identity without outshouting the active-state border. The
Claude Activity tab sets claudeAccent (#D97757) — nominative use per the
licenses.yaml trademark note (it marks Claude's own panel).

Filed and closed as a try-it-out (user request); trivially revertible if
the accent doesn't land visually.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/builtin/claude/src/extension.dart

@@ -5,6 +5,7 @@ import 'package:clide/clide.dart';
 import 'package:clide/builtin/claude/src/activity_cluster.dart' show foldLevelFromName, kActivityFoldLevelKey, nextFoldLevel;
 import 'package:clide/builtin/claude/src/claude_config.dart';
 import 'package:clide/builtin/claude/src/claude_status.dart' show nextSafePermissionMode;
+import 'package:clide/builtin/claude/src/conversation_view.dart' show claudeAccent;
 import 'package:clide/builtin/claude/src/claude_session_host.dart';
 import 'package:clide/builtin/claude/src/session_orchestrator.dart';
 import 'package:clide/builtin/claude/src/pane_context_status.dart';
@@ -308,6 +309,9 @@ class ClaudeExtension extends ClideExtension {
       slot: Slots.sidebar,
       title: 'Activity',
       icon: PhosphorIcons.byName('robot'),
+      // Claude's accent marks Claude's own panel in the rail (T-418) —
+      // nominative use per the licenses.yaml trademark note.
+      iconColor: claudeAccent,
       priority: 60,
       build: (_) => const ClaudeMetaSidebar(),
     ),