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(),
     ),

lib/extension/src/contribution.dart

@@ -27,6 +27,7 @@ class TabContribution extends ContributionPoint {
     required this.title,
     required this.build,
     this.icon,
+    this.iconColor,
     this.priority = 0,
     this.fileGlobs = const [],
     this.listenable,
@@ -39,6 +40,9 @@ class TabContribution extends ContributionPoint {
   final String title;
   final WidgetBuilder build;
   final Object? icon;
+
+  /// Optional identity tint for the icon-rail glyph (T-418).
+  final Color? iconColor;
   final int priority;
   final List<String> fileGlobs;
   final Listenable? listenable;

lib/src/shell/layout.dart

@@ -146,7 +146,7 @@ class _BottomRail extends StatelessWidget {
         return Container(
           color: tokens.chromeBackground,
           child: ClideIconRail(
-            items: [for (final t in tabs) ClideIconRailItem(id: t.id, icon: _iconFor(slot, t), tooltip: resolveTabTitle(ctx, t))],
+            items: [for (final t in tabs) ClideIconRailItem(id: t.id, icon: _iconFor(slot, t), tooltip: resolveTabTitle(ctx, t), iconColor: t.iconColor)],
             activeId: activeId,
             onSelect: (id) => kernel.panels.activateTab(slot, id),
           ),

lib/widgets/src/clide_icon_rail.dart

@@ -4,11 +4,16 @@ import 'package:clide/widgets/src/clide_tappable.dart';
 import 'package:flutter/widgets.dart';
 
 class ClideIconRailItem {
-  const ClideIconRailItem({required this.id, required this.icon, required this.tooltip});
+  const ClideIconRailItem({required this.id, required this.icon, required this.tooltip, this.iconColor});
 
   final String id;
   final ClideIconPainter icon;
   final String tooltip;
+
+  /// Brand/identity tint for this tab's icon (e.g. the Claude accent on the
+  /// Claude tab, T-418). Shown full-strength when active/hovered and slightly
+  /// dimmed when idle; null keeps the normal state colours.
+  final Color? iconColor;
 }
 
 class ClideIconRail extends StatelessWidget {
@@ -60,7 +65,10 @@ class _RailButton extends StatelessWidget {
         onTap: onTap,
         tooltip: item.tooltip,
         builder: (ctx, hovered, _) {
-          final color = active
+          final tint = item.iconColor;
+          final color = tint != null
+              ? (active || hovered ? tint : tint.withValues(alpha: 0.7))
+              : active
               ? tokens.globalForeground
               : hovered
               ? tokens.sidebarForeground