feat: AG-UI 协议对齐与路由导航功能

- 前端: 添加 SSE 流式支持、stateSnapshot 事件、路由导航工具
- 前端: 实现工具调用审批流程，支持 pending 状态展示
- 后端: Agent 状态管理与会话持久化相关重构
- 文档: 新增 agent-agui-full-alignance 设计文档
- 测试: 补充相关单元测试和集成测试

apps/test/features/chat/tool_registry_test.dart

@@ -1,4 +1,5 @@
 import 'package:flutter_test/flutter_test.dart';
+import 'package:social_app/features/chat/data/tools/route_navigation_tool.dart';
 import 'package:social_app/features/chat/data/tools/tool_registry.dart';
 
 void main() {
@@ -6,6 +7,10 @@ void main() {
     ToolRegistry.initialize();
   });
 
+  tearDown(() {
+    RouteNavigationTool.instance.clearNavigator();
+  });
+
   group('getTool', () {
     test('returns tool definition for create_calendar_event', () {
       final tool = ToolRegistry.getTool('create_calendar_event');
@@ -87,6 +92,33 @@ void main() {
       expect(result['location'], 'Room A');
       expect(result['endAt'], '2026-03-01T11:00:00Z');
     });
+
+    test('navigate_to_route rejects disallowed target', () async {
+      final result = await ToolRegistry.execute('navigate_to_route', {
+        'target': '/admin',
+      });
+
+      expect(result['ok'], false);
+      expect(result['error'], contains('not allowed'));
+    });
+
+    test('navigate_to_route executes allowed target when navigator is bound', () async {
+      String? navigatedTo;
+      bool replaced = false;
+      RouteNavigationTool.instance.bindNavigator((target, {replace = false}) {
+        navigatedTo = target;
+        replaced = replace;
+      });
+
+      final result = await ToolRegistry.execute('navigate_to_route', {
+        'target': '/settings',
+        'replace': true,
+      });
+
+      expect(result['ok'], true);
+      expect(navigatedTo, '/settings');
+      expect(replaced, true);
+    });
   });
 
   group('getAllTools', () {