Arcade drive mixed forward and turn onto the left stick, so one stick
commanded both track motors. Replaced with tank drive and moved the head
off the right stick onto the d-pad, so every control now maps to exactly
one motor.
- left stick Y -> left track (was: mixed into both)
- right stick Y -> right track (was: head tilt)
- d-pad U/D -> head tilt (was: right stick Y)
- d-pad L/R -> head turn (was: right stick X)
- Square/Circle -> left arm (was: d-pad U/D)
- Triangle/Cross-> right arm (unchanged)
- L2/R2 -> body lift (unchanged)
- L1+R1 together-> all stop (was: Circle)
Head is digital now rather than proportional, so HEAD_MAX drops to 45.
Stick X axes are unused. Also added a commented-out forgetBluetoothKeys()
call for clearing stale NVS pairings.