Raise the NPC character budget to 24k and refine the prototype neck

docs/blender-assets.md

@@ -141,7 +141,7 @@ render about 2.5 min.
 
 All library variants share the [character and gear asset contract](architecture.md#character-and-gear-asset-contract):
 `npc_base` mesh node, required 13 core bones (optional extras allowed), five
-tint slots, +Z visual front, 16,000/16,000 character budget and the same 256²
+tint slots, +Z visual front, 24,000/24,000 character budget and the same 256²
 slot-map/AO rules. Role selection and look notes:
 
 | Character | `layer_for()` / look | Suggested roles | Preview gear |
@@ -200,7 +200,7 @@ carry baked AO and the shared neutral material maps described above.
 
 - `python3 tools/blender_assets.py audit`: container, `POSITION`/`NORMAL`/
   `TEXCOORD_0`, UVs in [0, 1], no zero-area triangles (Godot warns about them
-  during LOD generation), budgets (characters 16000/16000, gear 1500, props 4000
+  during LOD generation), budgets (characters 24000/24000, gear 1500, props 4000
   triangles), grounding, and an editable `.blend`. For characters it also
   checks skinning, bones, slots, the `npc_base` mesh node and the height.
 - `tools/tests/test_blender_assets.py`: catalogue and contract consistency with