docs(assets): per-class production briefs + template + formal deferral register (T-1049)

The asset-brief template (scope/visual-reference/naming/gen-path/
acceptance, one page) and five real briefs — station walls, rural walls,
doors, floors, furniture/props — each citing its D-235 axis tokens and
palette.md register rows (or the D-257 toon default), conventions.md
naming/mask/footprint rules, and the image-gen -> glb-gen -> promotion
path with concrete acceptance counts. Doors carry the negative
no-state-frame-files constraint (runtime mechanism stays Phase 5);
furniture/props' first acceptance is promoting the three unpromoted
spike GLBs. deferred.md is the formal register for the T-1051 four
(lamp posts, barns, TVs, billboards) + cars/Q-067, with rationale and
revisit triggers — satisfying T-1051's own 'or record formal deferral'
deliverable. Child stories under T-961 are created lead-side at merge.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/assets/visual/README.md

@@ -26,6 +26,17 @@ Per **[D-244](../../../governance/decisions/architecture.md#d-244)**: the in-wor
 Naming, mask-sidecar, D-235-keyed texture, and multi-tile footprint
 conventions: [conventions.md](conventions.md).
 
+## Per-Class Briefs
+
+Each asset class entering production is gated on a one-page brief —
+[../briefs/](../briefs/) — covering scope, visual reference, naming,
+generation path, and acceptance (template: [../_templates/asset-brief.md](../_templates/asset-brief.md)).
+Briefed this batch (T-1049): [station walls](../briefs/station-walls.md),
+[rural walls](../briefs/rural-walls.md), [doors](../briefs/doors.md),
+[floors](../briefs/floors.md), [furniture/props](../briefs/furniture-props.md).
+Formally deferred (not briefed): lamp posts, TVs, billboards, barns, cars —
+see [../briefs/deferred.md](../briefs/deferred.md).
+
 ## Palette
 
 See [palette.md](palette.md) for art direction: camera (D-148 gameplay / D-019