Help wanted: add GitHub Actions example for local format checks

[zxyasfas]

User pain

Labs and classes may want local format checks in CI, but examples must avoid committing real papers or private templates.

Expected PR

• Add a small documented GitHub Actions example that uses synthetic input paths.
• Explain that real papers and generated DOCX/PDF outputs should not be committed.
• Keep the example optional and local-first.

Acceptance criteria

• The example is easy to copy into another repository.
• The privacy warning is explicit.
• Standard validation commands pass if repository files are touched.

Privacy

Use fake paths and synthetic fixtures only.