Robot lacks the waist clamp expected by the locked-waist policy
(mode_machine=6). Default Kp=28.5 is intentionally low to protect
gears against a physical lock, but without the clamp the waist flops
under dynamic loads (walking/running), causing backward tilt.
Bump waist_roll and waist_pitch Kp to 100, Kd to 5 so the motors
hold the waist rigid. Remove the 8-degree offset — the waist default
position is correct, it just couldn't hold it. Keep offset keys 7/8
available for tuning if needed. Remove temporary debug logging.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>