docs: fix some broken links (#1864)

* Rename BACKEND_TODO.md to TODO.md in documentation

* Update MCP Setup Guide link in CONTRIBUTING.md

* Update reference to config.yaml path in documentation

* Fix config file path in TITLE_GENERATION_IMPLEMENTATION.md

Updated the path to the example config file in the documentation.

CONTRIBUTING.md

@@ -310,7 +310,7 @@ Every pull request runs the backend regression workflow at [.github/workflows/ba
 
 - [Configuration Guide](backend/docs/CONFIGURATION.md) - Setup and configuration
 - [Architecture Overview](backend/CLAUDE.md) - Technical architecture
-- [MCP Setup Guide](MCP_SETUP.md) - Model Context Protocol configuration
+- [MCP Setup Guide](backend/docs/MCP_SERVER.md) - Model Context Protocol configuration
 
 ## Need Help?
 

backend/docs/AUTO_TITLE_GENERATION.md

@@ -248,7 +248,7 @@ def after_agent(self, state: TitleMiddlewareState, runtime: Runtime) -> dict | N
 - [`packages/harness/deerflow/agents/thread_state.py`](../packages/harness/deerflow/agents/thread_state.py) - ThreadState 定义
 - [`packages/harness/deerflow/agents/middlewares/title_middleware.py`](../packages/harness/deerflow/agents/middlewares/title_middleware.py) - TitleMiddleware 实现
 - [`packages/harness/deerflow/config/title_config.py`](../packages/harness/deerflow/config/title_config.py) - 配置管理
-- [`config.yaml`](../config.yaml) - 配置文件
+- [`config.yaml`](../../config.example.yaml) - 配置文件
 - [`packages/harness/deerflow/agents/lead_agent/agent.py`](../packages/harness/deerflow/agents/lead_agent/agent.py) - Middleware 注册
 
 ## 参考资料

backend/docs/TITLE_GENERATION_IMPLEMENTATION.md

@@ -30,7 +30,7 @@
 
 ### 2. 配置文件
 
-#### [`config.yaml`](../config.yaml)
+#### [`config.yaml`](../../config.example.yaml)
 - ✅ 添加 title 配置段：
 ```yaml
 title:
@@ -51,7 +51,7 @@ title:
 - ✅ 故障排查指南
 - ✅ State vs Metadata 对比
 
-#### [`BACKEND_TODO.md`](../BACKEND_TODO.md)
+#### [`TODO.md`](TODO.md)
 - ✅ 添加功能完成记录
 
 ### 4. 测试