bugfix：修复一些bug

app/main.py

@@ -17,6 +17,7 @@ from app.core.logging import setup_logging
 @asynccontextmanager
 async def lifespan(application: FastAPI):
     setup_logging()
+    from app.agent.screen_agent import get_screen_agent
     from app.clients.decision import close_decision_engine
     from app.clients.mcp import start_mcp_servers, stop_mcp_servers
     from app.clients.user_center import close_user_center
@@ -35,6 +36,11 @@ async def lifespan(application: FastAPI):
         await warm_material_cache(persistence.db)
         # 拉起 mcp_servers.json 中由应用管理的服务；单个服务失败只记录，用到它的请求执行时报错
         mcp_processes = await start_mcp_servers()
+        # 提前拉取 MCP 工具并组装 agent，问题在启动时暴露；失败只记录，首个请求会重试
+        try:
+            await get_screen_agent()
+        except Exception as error:
+            logger.opt(exception=error).error("screen agent 预先组装失败")
         application.state.agent_service = AgentService(
             build_graph(persistence.checkpointer), persistence.store
         )