An in-cluster GitHub Actions runner, registered with a one-hour registration token when you toggle it on and pointed at the repo you name in namespace settings.
With the runner on, the issue → PR loop is fully in-cluster: a labeled issue reaches its session's inbox in about five seconds, and the scheduled courier that empties the outbox runs right next to the fleet.
Delivery jobs use tiny deliver; the courier uses tiny export. Both are
the same binary you run on your laptop.