docs: add seminar scripts & assets, update Herdr guide and multi-agent documentation

docs/참고 자료.md

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+- https://twentytwentyone.tistory.com/454
+- Agent SDK
+	- [Claude](https://jjeongil.tistory.com/3360#google_vignette)
+	- [OpenAI](https://openai.github.io/openai-agents-python/)
+	- [Google ADK](https://github.com/google/adk-python)
+	- [Antigravity SDK](https://antigravity.google/product/antigravity-sdk)
+- [crewai a2a protocol](https://docs.crewai.com/v1.15.5/en/learn/a2a-agent-delegation)
+- [LangChain and LangGraph](https://www.youtube.com/watch?v=W_uwR_yx4-c)