labelWidget label; interactive widgets also use it for ID generation. A ## suffix can distinguish IDs without displaying the suffix.
vMutable checked state in Uint8Array[0]: 0 is unchecked, 1 is checked; activation toggles it in place. Pass Uint8Array storage, not a JS scalar; native access uses the supplied backing memory.
True if the widget changed the supplied value; false if it remained unchanged.
Display a checkbox that edits a Boolean value.