Replace sidebar logo with chevron icon

lib/app/app_shell_desktop.dart

@@ -8,7 +8,6 @@ import '../theme/app_palette.dart';
 import '../theme/app_theme.dart';
 import '../widgets/detail_drawer.dart';
 import '../widgets/pane_resize_handle.dart';
-import '../widgets/app_brand_logo.dart';
 import '../widgets/sidebar_navigation.dart';
 import 'app_controller.dart';
 import 'workspace_page_registry.dart';
@@ -470,8 +469,8 @@ class _SidebarRevealRailState extends State<_SidebarRevealRail> {
               boxShadow: _hovered ? [palette.chromeShadowLift] : const [],
             ),
             child: _hovered
-                ? DoorLogoIcon(
-                    side: DoorLogoSide.left,
+                ? Icon(
+                    Icons.chevron_right_rounded,
                     size: 16,
                     color: palette.textMuted,
                   )

lib/widgets/sidebar_navigation.dart

@@ -1,6 +1,5 @@
 import 'package:flutter/material.dart';
 
-import 'app_brand_logo.dart';
 import '../i18n/app_language.dart';
 import '../models/app_models.dart';
 import '../theme/app_palette.dart';
@@ -224,21 +223,64 @@ class SidebarHeader extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final content = AppBrandLogo(
+    final content = _SidebarHeaderChevron(
       size: isCollapsed ? 36 : 28,
       borderRadius: isCollapsed ? 10 : 8,
     );
+    final alignedContent = Align(
+      alignment: Alignment.centerRight,
+      child: content,
+    );
 
     if (onTap == null) {
-      return content;
+      return alignedContent;
     }
 
     return Tooltip(
       message: appText('展开导航', 'Expand sidebar'),
-      child: InkWell(
-        borderRadius: BorderRadius.circular(AppRadius.button),
-        onTap: onTap,
-        child: Padding(padding: EdgeInsets.zero, child: content),
+      child: Align(
+        alignment: Alignment.centerRight,
+        child: InkWell(
+          borderRadius: BorderRadius.circular(AppRadius.button),
+          onTap: onTap,
+          child: Padding(padding: EdgeInsets.zero, child: content),
+        ),
+      ),
+    );
+  }
+}
+
+class _SidebarHeaderChevron extends StatelessWidget {
+  const _SidebarHeaderChevron({required this.size, required this.borderRadius});
+
+  final double size;
+  final double borderRadius;
+
+  @override
+  Widget build(BuildContext context) {
+    final palette = context.palette;
+    return Container(
+      width: size,
+      height: size,
+      decoration: BoxDecoration(
+        gradient: LinearGradient(
+          begin: Alignment.topLeft,
+          end: Alignment.bottomRight,
+          colors: [
+            palette.chromeHighlight.withValues(alpha: 0.9),
+            palette.chromeSurface,
+          ],
+        ),
+        borderRadius: BorderRadius.circular(borderRadius),
+        border: Border.all(color: palette.chromeStroke),
+        boxShadow: [palette.chromeShadowAmbient],
+      ),
+      child: Center(
+        child: Icon(
+          Icons.chevron_right_rounded,
+          size: size * 0.72,
+          color: palette.textSecondary,
+        ),
       ),
     );
   }

test/widgets/sidebar_navigation_suite.dart

@@ -6,6 +6,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:xworkmate/i18n/app_language.dart';
 import 'package:xworkmate/models/app_models.dart';
 import 'package:xworkmate/theme/app_theme.dart';
+import 'package:xworkmate/widgets/app_brand_logo.dart';
 import 'package:xworkmate/widgets/sidebar_navigation.dart';
 
 void main() {
@@ -154,4 +155,35 @@ void main() {
       expect(selected, WorkspaceDestination.settings);
     },
   );
+
+  testWidgets('SidebarNavigation header uses chevron instead of brand logo', (
+    WidgetTester tester,
+  ) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: AppTheme.light(),
+        home: Scaffold(
+          body: SidebarNavigation(
+            currentSection: WorkspaceDestination.assistant,
+            sidebarState: AppSidebarState.expanded,
+            appLanguage: AppLanguage.zh,
+            themeMode: ThemeMode.light,
+            onSectionChanged: (_) {},
+            onToggleLanguage: () {},
+            onCycleSidebarState: () {},
+            onExpandFromCollapsed: () {},
+            onOpenHome: () {},
+            onOpenAccount: () {},
+            onOpenThemeToggle: () {},
+            accountName: 'Tester',
+            accountSubtitle: 'Workspace',
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.byIcon(Icons.chevron_right_rounded), findsOneWidget);
+    expect(find.byType(AppBrandLogo), findsNothing);
+  });
 }