Extend the v0.6.0 plan with the Blender asset library

Document the larger asset set produced by the running Blender generator
(tools/blender_assets.py): 8 NPC character variants, 18 gear pieces, and 22
street/venue props with a manifest, editable sources, and preview sheets.

- TODO gains Phase 3.5 with the audit/budget reconciliation (npc_casual is
  currently 7,756 tris / 5,616 verts, above the 6,000/4,000 contract), character
  selection by role, gear attach points, prop replacement/placement, emissive
  wiring, budgets, and screenshot gates
- PLAN's Visual Quality Direction describes the library, runtime selection, and
  offline fallbacks
- docs/plan-graphics-v0.6.md adds the library contract/output table and
  integration steps, and points Phase 4 at the Blender props
- MEMORY records the manifest-as-source-of-truth rule and the generator caveat

Generated library files stay untracked until the running build finishes and
passes the audit; the generator itself is committed so the plan is reproducible.

MEMORY.md

@@ -129,6 +129,15 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
   flat plane, so avoidance (not a baked mesh) routes guests around props. Placements live in
   `PROP_PLACEMENTS` with `placement_problems()` validation; variants come from `variant_for(index)`.
   `smoke_props.gd` must be windowed because the guard reads captured-mouse input.
+- **Blender asset library (v0.6.0, in progress):** `tools/blender_assets.py` generates
+  `assets/models/blender/{npc,npc_gear,props}/` plus `manifest.json`, `docs/blender_previews/`,
+  and (when finished) `docs/blender-assets.md`. Contract: 8 character variants (same bones/slots
+  as `npc_base`), 18 gear pieces in attach-point space (head/hand/back/chest), 22 props; the first
+  nine replace current furniture/lamps/trees/cone, the rest are new dressing. Treat the manifest
+  as the source of truth and run `python3 tools/blender_assets.py audit`/`sheet` before wiring.
+  At the time of writing only `npc_casual` existed (7,756 tris / 5,616 verts, above the current
+  6,000/4,000 character budget) — reconcile the budget before integration. Don't edit the
+  generator while its Blender process is running.
 - **Prop pipeline (done):** audit enforces 400 tris / 600 verts, ground contact, UV range, no
   degenerate tris, one material. `capture_prop_gallery.gd` writes `10-prop-gallery.png` (3x2 studio
   line-up, back row on a platform) and the `prop_gallery` catalogue entry compares it.