Branch protection on main requires three status checks:
- CI / lint (pull_request) [was already satisfied]
- CI / ci (pull_request) [new: validates JSON files]
- Promotion Gate / Promotion Gate (pull_request) [new: validates skills structure]
Adding the ci job and Promotion Gate workflow so all required checks
can pass on PRs, unblocking future merges to main.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
