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

AGENTS.md

@@ -91,8 +91,8 @@ specialists the task needs:
 ### Project rules that override a skill
 
 1. **The project contract wins.** `npc_base` mesh node, the 13 required core bones at their rest
-   positions, five tint slots, front on Blender −Y / Godot +Z, grounded feet, 16,000
-   triangles / 16,000 glTF vertices per character, 1,500 per gear, 4,000 per prop. Optional
+   positions, five tint slots, front on Blender −Y / Godot +Z, grounded feet, 24,000
+   triangles / 24,000 glTF vertices per character, 1,500 per gear, 4,000 per prop. Optional
    extra bones (fingers, face, toes) are allowed if they do not move the core rest positions. A skill
    may recommend another topology, naming or budget scheme; do not adopt it unless the
    change is explicitly planned and the contract, tests and docs are updated together.