os-rust-backend-ci

Use this skill when the user wants to set up, configure, debug, or extend a GitHub Actions pipeline for a Rust backend that runs CI checks and produces a container image artifact in GHCR. Scope is testing + artifact only — deployment is intentionally out of scope. Trigger on: PR checks (fmt, clippy, tests, OpenAPI / contract drift) for a Rust API; build-and-push on push-to-main; tagging images :<short-sha> plus mutable :staging / :production pointers in GHCR; a manual promote workflow that re-tags an existing image instead of rebuilding (build-once); rollback by re-promoting an older SHA; configuring GHCR_TOKEN / packages: write permissions; debugging api.yml, build-api.yml, promote.yml, or the setup-rust / changed-paths composite actions. Also trigger for vaguer phrasings like "set up CI for our notes-api", "immutable image refs with manual promote", or any image-tag-promotion / staging-then-production artifact pipeline on a Rust + GHCR stack. Do not trigger for non-Rust backends or generic Docker / CI questions.