feat: Agent 运行时、对话 API、作业助手与引擎修复及前端执行超时

- agent_runtime 模块与 agent_chat API，前端 AgentChat 视图与路由对接
- workflow_engine: code 节点命名空间与 json 引用修复
- llm_service: 工具调用 extra_body（如 DeepSeek）
- create_homework_manager_agent / _3 脚本与测试脚本扩展
- frontend: WORKFLOW_EXECUTION_HTTP_TIMEOUT_MS、AgentChatPreview/MainLayout 等
- 文档：架构说明与自主 Agent 改造完成情况

Made-with: Cursor

backend/app/main.py

@@ -201,7 +201,7 @@ async def startup_event():
         # 不抛出异常，允许应用继续启动
 
 # 注册路由
-from app.api import auth, uploads, workflows, executions, websocket, execution_logs, data_sources, agents, platform_templates, model_configs, webhooks, template_market, batch_operations, collaboration, permissions, monitoring, alert_rules, node_test, node_templates, tools
+from app.api import auth, uploads, workflows, executions, websocket, execution_logs, data_sources, agents, platform_templates, model_configs, webhooks, template_market, batch_operations, collaboration, permissions, monitoring, alert_rules, node_test, node_templates, tools, agent_chat
 
 app.include_router(auth.router)
 app.include_router(uploads.router)
@@ -223,6 +223,7 @@ app.include_router(alert_rules.router)
 app.include_router(node_test.router)
 app.include_router(node_templates.router)
 app.include_router(tools.router)
+app.include_router(agent_chat.router)
 
 if __name__ == "__main__":
     import uvicorn