[j321m]

• New workflow .github/workflows/black.yml: on every PR to main, installs black==25.1.0 (same pin as pixi.toml) and runs black --check --diff .. It uses pip rather than pixi, so it takes seconds instead of installing torch.
• New pyproject.toml with only [tool.black] extend-exclude = "^/third_party/", so local runs skip the vendored LiveCodeBench too.

Merge after the fixes PR (janek/fixes): main still has 4 unformatted files, and that PR formats them.

After merging, make the check required: Settings → Branches → rule for main → "Require status checks to pass" → black.