[FEATURE] Add example for multi-agent collaboration

[981526092]

Feature Description

It would be helpful to have an example showing how multiple agents can collaborate on a complex task (e.g., research agent + summarization agent).

Use Case

I'm working on Track A and want to build a multi-agent system, but I'm not sure how to coordinate between agents using LangGraph.

Suggested Implementation

• Add tutorials/09_multi_agent_collaboration.ipynb
• Show state management between agents
• Include cost tracking for multiple agents

Alternatives Considered

• Looking at Track A examples, but they focus on single agents
• Checked LangGraph documentation, but need hackathon-specific example

Additional Context

This would be especially useful for teams building complex systems for Track A (performance) and Track B (observability).