GitHub Actions cancel-in-progress: build each new SHA on its own ref

If a workflow uses concurrency: group: name-${{ github.ref }} with cancel-in-progress, dispatching again on the same ref cancels the build already running there. To keep an old build running as a compile check while testing a newer commit, push the new SHA to a fresh ref (e.g. ci/feature2) and dispatch there. Also make sure only one actor dispatches. A lead and a sub-agent dispatching the same ref seconds apart cancelled one of the two runs; it was still queued, so no real build was lost. Before dispatching, check git ls-remote origin 'refs/heads/ci/<name>*' and gh run list --branch <ref>, and tell other agents explicitly who owns the dispatch.