My CI Runner Was Killed by My Own Script: The Dark Side of Cleanup

Towards the end of last month, I started a build job on my self-hosted GitHub Actions runner. It was a job that normally took 10-15 minutes, but this time it just wouldn't finish. The job seemed stuck, and I wasn't getting any response from the runner. When I tried to connect to the server via SSH, the connection was refused. It felt similar to the OOM scenarios I'd experienced on my VPS where sshd couldn't accept connections, but this time my RAM usage was normal. After some digging, I realized