Record the tmp/npc-parts working-set layout decision

docs/3d-model-review.md

@@ -201,6 +201,13 @@ capture). Pass conditions:
 tests, the 48-frame baseline and the 96-frame pose/context review all stay authoritative; the new
 face/hands captures are the visual bar for this track.
 
+### Working-set layout
+
+Part sources and preview GLBs live under `tmp/npc-parts/<variant>/` (gitignored by the root
+`tmp/` rule); only the assembled character GLBs, AO/maps, the manifest and the review sheets are
+committed. No new committed `.blend` source tree is added without a docs/ADR decision — the
+frozen `npc_base.blend` stays the only tracked `.blend`.
+
 ## Scorecard skeleton
 
 Verdicts use `qa-review` semantics: **P0** (blocker: wrong scale, broken normals, budget fail),