Log in with a key

# run from: the repo root
./devkit ssh-key            # idempotent; --check reports whether it is done
ssh fishball

It creates ~/.ssh/fishball, a key used for nothing else (the board has a published root password), installs it on the board, adds a Host fishball block to ~/.ssh/config, and proves it by logging in with the key alone.

The password stays enabled. Turning it off, and the risk of locking yourself out: networking reference.