An SSH Deploy Key for CI That Can Only Run Two Commands: authorized_keys command= and SSH_ORIGINAL_COMMAND
CaRMen's deploys start in GitHub Actions and end on a server, and something has to cross that gap. Here it's an SSH key, stored as a secret in the repository, that the deploy job uses to connect to the server and run the deploy. A key like that is exactly the kind of secret that leaks: it sits in a CI system, it's used automatically, and nobody watches each use. So the key can't open a shell.