Clean / update LangGraph Tutorial

[rlancemartin]

Update, clean, and improve LangGraph cookbooks.

[IgorKasianenko]

Thanks for the PR! Let me check with the team who can review it.

[rlancemartin]

Thanks for the PR! Let me check with the team who can review it.

Thanks! @jeffxtang may be able to have a look. Also I can add llama4; should be a quick change / waiting for Groq to offer Maverick.

[jeffxtang]

Thanks @rlancemartin for the PR. I can successfully run langgraph_rag_workflow but running langgraph_tool_calling_agent on my local jupyter on the code

messages = [HumanMessage(content="Generate an image based upon this text: 'a yellow lab puppy running free with wild flowers in the mountain behind'")]
messages = agent.invoke({"messages": messages}, config=config)

gave me an error (not sure if it's caused by replicate):

If you can fix the error and also get the notebooks updated for Llama 4 (I saw Groq now offers both Maverick and Scout) that'd be great.