Submit a preparation step using its typed material contract and current revision; acceptance is not approval

Direct API option only. Permission: card.holder.preparation. Body: type=holder, id=steps[].id, current revision, complete values snapshot (not PATCH). Use attachment fileIds and requirements field keys. No draft request is needed. Acceptance is not bank approval: next poll GET /cards/preparation until isPrepared=true. On 201024 refresh revision; on 201025 wait/follow state instead of forcing edits.