fix(mcp): migrate from deprecated create_react_agent to create_agent

- Replace langgraph.prebuilt.create_react_agent with langchain.agents.create_agent

- Update parameter from prompt/state_modifier to system_prompt

- Remove unnecessary signature introspection (new API is stable)

- Follows LangChain v1 / LangGraph v1 migration guide

Author: gitwalter

README.md

@@ -3,7 +3,6 @@
 **A pedagogical toolkit for building AI agent systems with practical software development techniques.**
 
 ![Python](https://img.shields.io/badge/Python-3.8+-blue?style=flat-square)
-![License](https://img.shields.io/badge/License-MIT-green?style=flat-square)
 ![Status](https://img.shields.io/badge/Status-Research%20Foundation-orange?style=flat-square)
 
 ---
@@ -190,12 +189,6 @@ See [CONTRIBUTING.md](./CONTRIBUTING.md) for detailed guidelines.
 
 ---
 
-## License
-
-MIT License - see [LICENSE](./LICENSE) for details.
-
----
-
 ## Acknowledgments
 
 Built with: