Currently only SIGINT (Ctrl+C) triggers a graceful shutdown, however, it would make sense for SIGHUP and SIGTERM to have this behavior as well. Maybe others.

For example, using the provided docker-compose.yaml with docker-compose up and later docker-compose down will leave the system in a dirty state and all workspaces will be left running.

We can probably just extend the SIGINT behavior to listen to these two signals. After any one of them is received, either deregister HUP and TERM or add an exit handler.