Agent Skills: actions-optimiser

Use when the user wants to optimise or review a GitHub Actions workflow file (.github/workflows/*.yml), find real-world examples of how a specific action like `hashicorp/setup-terraform` is used in other repos, or compare their workflow against community patterns. Triggers on "optimise this workflow", "how do others use <action>", "review my GitHub Actions", "find examples of <action>". Not for non-GitHub CI (CircleCI, GitLab CI, etc.).