gfcloud runs the machine under the Glowforge web service (the factory
cloud experience: the app drives homing, framing, printing). Its init
service starts it only when controller_mode = cloud - mutually exclusive
with grblHAL, which already stands down for that mode - so it owns
/dev/glowforge exclusively. Persistent GFUIService loop with a clean
SIGTERM shutdown that safes the hardware; the init script mirrors
grblhal.init. The image installs gfcloud and python3-ffmachine.
