Add a validate_fn hook to SwitchDesc, checked in switch.py before dispatch
and surfaced as a ServiceValidationError so an unsupported write shows a
real error in the UI instead of the coordinator's silent log-only rejection.
Wired it into the three course-gated washer switches using their
availability bitmaps (BubbleSoakSet/PreWashAvailableSet/IntensiveAvailableSet),
which line up positionally with editCourseList. Turning a toggle off is
never blocked, and the check fails open whenever the course or bitmap can't
be resolved.
Also fixes a bug in _bool_option_write: it took a `p and 'On' or 'Off'`-style
truthy check, but switch.py always calls it with the string 'On' or 'Off' --
both truthy, so every write landed as 'On' regardless of intent.
Marc Billow
f54daf3608