Validate Binder and notebook quickstart path

[weich97]

Scope

Run the Binder or Colab notebook path and record any fixes needed for a clean five-minute experience.

Suggested files

• notebooks/tradearena_5min_colab.ipynb
• binder/requirements.txt
• docs/getting_started.md

Acceptance criteria

• Notebook runs the deterministic benchmark path.
• Notebook computes a trajectory hash.
• Docs mention any environment-specific caveats.

Validation

tradearena --benchmark tradearena-core --periods 30 --output outputs/examples/notebook_trajectory.json
tradearena hash-run outputs/examples/notebook_trajectory.json