Start the challenge $0.
Run the following command in the background (it may block waiting for init tasks):
sh
labctl challenge start $0 --no-open --no-ssh
The --no-open flag prevents opening the browser.
The --no-ssh flag prevents starting an interactive SSH session.
Since this command may take a long time (it waits for all init tasks to complete),
run it in the background and immediately use the list-running-playgrounds skill
to find the playground ID for further operations.