ObjectManager._upload_action_async is the single entry for every action
path (setters, direct edits of the public action array, run()). It now
also rejects nonzero vx/vy/omega slots of Jet-driven bodies via
validate_jet_motion, before any device copy. Regression: each motion
slot edited directly is rejected with no device write; zero motion
uploads. Simulation.set_jet_amplitude documents that a device error
requires close/recreate, as for other CUDA exceptions.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
