The healthcheck's `journalctl --user` command fails with "No journal
files were opened due to insufficient permissions" for runner users
that lack journal access. This caused the healthcheck to always report
"OK: runner healthy" even when all runners were unregistered — the
auto-recovery never triggered.
Replace journal-based detection with a Gitea API query: read the
runner's ID from the .runner file and verify it exists in
GET /api/v1/admin/actions/runners. This works regardless of journal
permissions.
Also add scripts/cleanup_stale_runners.py for bulk cleanup of stale
runner registrations (runners that haven't been online for a
configurable threshold).
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
