RFD 1046: Model image for skintokens_auto_rig
Problem
SkinTokens is the default auto rig. It writes a skeleton and skin weights for a mesh that has neither.
A rig is the clearest case for RFD 1053. The rig is an opinion about an existing mesh, and a flat file forces the rig stage to rewrite the mesh to carry it.
Decision
Write the rig as a USD layer over the mesh layer. UsdSkel holds the skeleton, the joint order, and the binding. The mesh layer below stays untouched.
Emit VRM beside it, because the client needs VRM humanoid tracks.
See DETAILS.md for the model’s memory, the predict() interface, why UsdSkel beats a GLB skin, and the joint order trap between VRM and USD.