refactor: 重构 AgentScope ReAct Runner 与事件处理

- 重构 runtime/runner.py 实现 ReAct Agent 核心逻辑
- 更新事件编码器与存储机制
- 优化 prompt 系统与 tool 调用
- 调整 agent service 与 repository 配合

backend/src/core/agentscope/tools/custom/calendar.py

@@ -1,5 +1,3 @@
-from __future__ import annotations
-
 from datetime import datetime, timedelta, timezone
 from typing import Annotated, Any, Literal, cast
 from uuid import UUID

backend/src/core/agentscope/tools/custom/user_lookup.py

@@ -1,5 +1,3 @@
-from __future__ import annotations
-
 from typing import Annotated, Any, cast
 from uuid import UUID