Configs and updates to gaia eval

• Use tool calling
• Eval Apriel model
• Added readme

Description by Korbit AI

What change is being made?

Update Gaia evaluation configs and flow to use Apriel 1.5 LLM, switch to function-call style guidance, extend max_turns settings, and wire LLM endpoint configuration via environment variable; rename action class, adjust Gaia Gym/Benchmark wiring, and add supporting experiment/docs.

Why are these changes being made?

Switch to an Apriel-based evaluation setup with function-call style guidance to improve tool use and reliability; expose LLM base URL via environment for flexibility; extend max_turns to better control evaluation length and align env creation with new config fields; and update docs to guide setup.

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