Cost Metrics added

[xzrderek]

notes on tracking in frameworks:

• pydantic ai cost tracking is tricky, when we make a call to their multi-agent framework, response doesn't tell you which model used how many tokens, it's all aggregated. let's chat about it when you're back @dphuang2
• didn't see a langgraph example so couldn't fully test it, but added commented out code for it. need to test once example is in next week @benjibc