Trigger position now sets arm ANGLE rather than power, via
setAbsoluteMotorPosition with BrakingStyle::HOLD. Encoders are zeroed on
hub1 connect, so both arms must be down at that moment.
Spans measured with tools/arm_calibrate: roughly +280 left, -275 right,
both comfortably under one motor revolution so the absolute encoder is
unambiguous. Set to +/-250 to keep backlash clear of the end stop.
L3/R3 are no longer bound - releasing the trigger is lowering.
Also documents the async-init trap in serviceHub.
jessikitty
343544510f