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

docs/3d-model-review.md

@@ -193,7 +193,7 @@ capture). Pass conditions:
 
 ### Contract (both, every prototype)
 
-- 16,000 triangles / 16,000 glTF vertices per character; gear stays at 1,500.
+- 24,000 triangles / 24,000 glTF vertices per character; gear stays at 1,500.
 - Optional extra bones are allowed; the required 13 core bones and their rest positions must not
   move; the `npc_base` mesh node name and the five tint slots stay unchanged.