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/lib/features/chat/data/models/tool_result.g.dart

@@ -21,7 +21,7 @@ Map<String, dynamic> _$ToolResultToJson(ToolResult instance) =>
 
 UiCard _$UiCardFromJson(Map<String, dynamic> json) => UiCard(
   cardType: json['type'] as String,
-  schemaVersion: json['version'] as String? ?? 'v1',
+  schemaVersion: json['version'] as String? ?? _defaultSchemaVersion,
   data: json['data'] as Map<String, dynamic>,
   actions: (json['actions'] as List<dynamic>?)
       ?.map((e) => CardAction.fromJson(e as Map<String, dynamic>))