For pull requests, check-recent now runs a single job (ubuntu-latest,
r-release) via a setup job that emits the matrix as JSON. On push and
schedule the full matrix is unchanged (devel + release on all OSes,
oldrel-1 through oldrel-4).
Also removed the pull_request trigger from check-recent-dev-pkgs; the
dev-packages check only needs to run on push/schedule.
https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b
