Extends slash-commands with a new /stageblog command that lets authorized
maintainers trigger a workflow_dispatch for staging blog previews from fork
PRs, where the normal pull_request-triggered preview cannot access secrets.
- Captures pr.head.sha at comment time and passes it to the dispatched
workflow so fork authors cannot push new commits between review and build
- Disabled unless stageblog-workflow input is set
- Refuses with stageblog-not-blog result if no changed file matches
stageblog-paths (default blog/**)
- Documents companion workflow pattern, additional PAT scope (Actions:
write), and SHA-pinning safety requirement
Move the handler logic out of the YAML script block into a standalone
main.js loaded via require(GITHUB_ACTION_PATH). This improves
readability and makes the JS easier to lint and unit-test directly.
