refactor(chat): 重构聊天模块并集成历史消息加载功能

- 删除冗余的 chat_history_repository 和 home_mock_data
- 简化 ag_ui_event fromJson 使用工厂映射表
- 提取 ChatBloc 事件处理方法，添加 loadHistory/loadMoreHistory
- HomeScreen 集成 ChatBloc 实现历史消息加载和下拉刷新
- 更新 AGENTS.md 文档约束

apps/test/features/home/ui/screens/home_screen_test.dart

@@ -2,51 +2,33 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:lucide_icons/lucide_icons.dart';
 import 'package:social_app/features/home/ui/screens/home_screen.dart';
-import 'package:social_app/shared/widgets/chat_bubble.dart';
 
 void main() {
   group('HomeScreen Widget Tests', () {
-    testWidgets('displays chat messages with ChatBubble', (
-      WidgetTester tester,
-    ) async {
-      await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
-
-      expect(find.byType(ChatBubble), findsAtLeastNWidgets(1));
-    });
-
-    testWidgets('displays user request message', (WidgetTester tester) async {
-      await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
-
-      expect(find.textContaining('明天提醒我开会'), findsOneWidget);
-    });
-
-    testWidgets('displays AI response message', (WidgetTester tester) async {
-      await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
-
-      expect(find.textContaining('已为你创建日程'), findsOneWidget);
-    });
-
-    testWidgets('displays calendar schedule cards in chat flow', (
-      WidgetTester tester,
-    ) async {
-      await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
-
-      expect(find.byType(ChatBubble), findsAtLeastNWidgets(2));
-    });
-
-    testWidgets('input field is present', (WidgetTester tester) async {
+    testWidgets('displays input field', (WidgetTester tester) async {
       await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
+      await tester.pumpAndSettle();
 
       expect(find.byType(TextField), findsOneWidget);
       expect(find.text('输入消息...'), findsOneWidget);
     });
 
-    testWidgets('header icons are present', (WidgetTester tester) async {
+    testWidgets('displays header icons', (WidgetTester tester) async {
       await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
+      await tester.pumpAndSettle();
 
       expect(find.byIcon(LucideIcons.settings), findsOneWidget);
       expect(find.byIcon(LucideIcons.calendar), findsOneWidget);
       expect(find.byIcon(LucideIcons.messageSquare), findsOneWidget);
     });
+
+    testWidgets('displays send or mic icon based on input', (
+      WidgetTester tester,
+    ) async {
+      await tester.pumpWidget(const MaterialApp(home: HomeScreen()));
+      await tester.pumpAndSettle();
+
+      expect(find.byIcon(LucideIcons.mic), findsOneWidget);
+    });
   });
 }