[anHappyDog]

Summary

Apply the commit policy from EmbodiRun PR #9: Conventional Commits 1.0 subjects, a 72-character subject limit, the same eleven categories, and DCO 1.1 sign-offs matching each commit's author and named human coauthors. PR titles follow the same subject rules. The contribution guide documents categories, scopes, breaking changes, layout, and repair commands; the PR checklist links to the policy.

Add Commit policy as a separate CI job in its own workflow. It needs only Git and Python's standard library, checks every introduced commit (including contributor-created merges), and reruns on PR edits without rerunning the CPU/lint/docs workflow. It uses the event's actual base/head range and Git's trailer parser; existing main history and GitHub's temporary test-merge commit are excluded.

Verification

• python -m pytest tests/test_commit_policy.py -q: 20 passed using real temporary Git histories. Covers unsigned earlier commits, author mismatch, invalid/nonterminal trailers, coauthors, merges, invalid messages, PR title/event handling, and missing/empty ranges.
• ruff check scripts/check_commit_policy.py tests/test_commit_policy.py: passed.
• ruff format --check scripts/check_commit_policy.py tests/test_commit_policy.py: passed.
• mkdocs build --strict and mkdocs build --strict -f mkdocs.zh.yml: passed.
• git diff --check: passed.
• GitHub CI: 566 passed, 93 skipped; lint and strict EN/ZH documentation builds passed.
• Live negative title check: an invalid PR title failed as expected; restoring the compliant title passed. Only the independent policy workflow reran on these edits.

Hardware: CPU only. Weights: none. Numerical parity: not applicable; no inference, engine, policy, backend, dependency, or lock-file changes.

Rollout

Main's branch protection now requires Commit policy from the GitHub Actions app. The existing two-review requirement, stale-review dismissal, and enforcement for administrators are preserved; this check does not add a requirement for branches to be up to date.

Merge this PR to make the workflow available to other PRs. Existing PRs need a fresh policy run (for example, by updating their branch or reopening the PR) and must fix any violations; merged history is not rewritten. Maintainers must retain the contributors' DCO trailers and use compliant final commit messages when squashing, rebasing, or creating a merge commit, since the PR job cannot inspect a future GitHub-generated commit.

Checklist

• The PR title and introduced commit follow the policy and have the author's DCO sign-off.
• Contribution is licensed under Apache-2.0.
• Existing CPU/lint/docs jobs are unchanged; only the requested independent policy job is added.