[codex] Add LegalBenchPro CI and oversight framing

[EternWang]

What changed

• Added pyproject.toml so pytest can discover the src/ package layout without manual PYTHONPATH setup.
• Added a GitHub Actions CI workflow that installs dependencies, runs python -m pytest -q, and compiles scripts and src on Python 3.11 and 3.12.
• Added a README section on relevance to human-AI oversight, highlighting annotation protocols, human validation staging, audit trails, model failure analysis, and reproducible collaboration.
• Added pytest>=8 to requirements.txt so the documented validation command works after installing project requirements.

Why

This makes the public LegalBenchPro repository easier for reviewers and collaborators to inspect quickly, especially for human-AI complementarity and scalable oversight applications.

Validation

• python -m pytest -q
• python -m compileall scripts src