The fixed front-axis rotation degenerated on poses with the arms bent
forward (vector nearly parallel to the axis — why the mannequin showed
no effect on salsa-like moves). The swing axis is now computed per
frame as cross(current arm direction, character outward side), so the
arm is always pushed away from the torso regardless of the pose, and
the rotation naturally vanishes once the arm already points outward.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
