OSC DEV V006 Rev B Is Ready

Rev A took board surgery to power on. Then I hit an RX line that refused to go LOW . Then I noticed a third defect I never wrote up: the differential current sensing on the OPA wasn't actually differential. Rev B is the respin that fixes all three, plus a handful of features I was going to need anyway. If you're new here, OpenServoCore is my effort to turn cheap MG90S-class servos into networked smart actuators with sensor feedback, cascade control, and a DYNAMIXEL-style TTL bus. The CH32V006 de