[merynz]

Product integration slice — issue #361

Pre-edit audit completed against main ffcbaa9ca68a31bda0c07511fcb886556941c1a0, #297/#352/#353 and #363/#364/#365. No Graphics, Corpus370 or model research edits.

• Import unchanged V6 Mechanics CAS executor from pinned AXIS V6: control-ready rig program + SkinCode product contracts #297 (dd3089957e3126d93db4ad2804e30511cfdca348), original blob a1f4a66e2e67fbce150649a4feaae426cfa966d0.
• Add explicit RealSaS.ProductMechanicsCompile.v1 MODULE route to current Platform worker; no change to existing V1 roles, stage routing or Go graph registration.
• Add real synthetic artifact-bound CAS read/qualification/serialized output and direct async worker dispatch tests; negative tests cover duplicated/mismatched inputs, independent Skin deform lineage, wrong contract and forbidden ModelRelease.
• Record scope, proof boundaries and prerequisite V2 producer chain at docs/platform/MECHANICS_CAS_REST_WORKER_MAINLINE_20261107.md.

Scientific / product boundary

Not product-ready: main Go capabilities still emit Rig/Skin v1, while Mechanics requires v2. This PR intentionally does not register product.mechanics; the developer-only node must wait for V2 producer entrypoints and tests. PASS here is rest-only qualification of the supplied typed artifacts; not 6D editing, behavior proof, source↔canonical parity, Graphics, animated .rss, unseen or ProductRevision.

Do not merge until: exact-head dedicated worker tests, Platform/Go and current-mainline/broad regressions pass and review verifies no unintended registration or promotion. This branch is short-lived and based directly on canonical main. Related #365 Motion V2 remains independent.