ci: check English commit messages with one-time PR reminders

[youzi-1122]

Summary

Validate PR titles and every commit message against Conventional Commits and reject Han characters. Run the metadata-only check on PR creation, pushes, and edits, and publish commit-policy on the PR head commit.

Post one fixed English reminder on the first failure. Later failures, fixes, and regressions update only the status and run summary. Serialize runs per PR to avoid duplicate reminders and reject results when the PR changes during validation.

Validation

• make test-commit-policy passes, covering title and commit validation, stale PR state, API errors, incomplete commit lists, and the first-failure / repeated-failure / fix / regression notification sequence.
• Workflow YAML parsing and git diff --check pass.
• No PR code is checked out or executed by the privileged workflow.

Rollout

After merge, the workflow runs on subsequent matching PR events. Existing PRs need a matching event to receive their first result. An administrator must add commit-policy as a required status check to enforce the merge gate. The check rejects Han characters; it is not semantic English language detection.

Author confirmation

• I have read and agree to the project contribution guide. Guide: https://github.com/ongridio/ongrid/blob/main/CONTRIBUTING.md