Validate the rendered mechanism

A CAD interference sweep does not validate a browser's scene graph. Establish independent mechanical intent, capture the actual rendered transforms, and compare them before claiming the simulation is correct.

1. Inventory all moving joints and components, including shafts/rotors, stationary housings, feed mechanisms, helper geometry and scene attachments. Record ownership, units, axis handedness, home datums and parent chains from CAD source or inspected geometry. Do not take the expected pivots from the suspect animation manifest.
2. Read the trace protocol. Build a reference with at least four noncoplanar landmarks per component. Drive the real renderer using cad-agent motion-trace reference.json --poses-only, then capture actual mesh vertices through its current world matrices in the common assembly frame, in mm.
3. Run cad-agent motion-trace reference.json capture.json --output motion-report.json. Inspect the worst-point, pivot-anchor and radial errors. Compare axes to physical shaft/bearing geometry; rest-pose agreement and rigid within-mesh distances alone cannot catch a wrong orbit. Keep fixed housings attached to their support.
4. Add captures for firing/operation, combined independent joints, stop/start, repeated cycles and scene transitions. Reproduce a wrong pivot with correct home placement and require failure. Also exercise units, axis/sign, lost-parent and ownership errors. Keep regression checks in the existing product build/test harness.
5. Pair kinematic checks with CAD motion/containment gates and visual inspection of the actual published renderer. Record input/export hashes, tolerance, sample density, untested events and independent reference provenance. A passing trace says nothing by itself about continuous clearance, loads, physical fit or hardware safety.

Use the repository's normal independent review and deployment process. This skill adds no publication permission.