Refine the head prototype: flatten face plane, taper jaw, nose/chin relief, fix ear-displacement sign

TODO.md

@@ -85,10 +85,10 @@ the rest of §C remains the broad review checklist.
       readable nose bridge/tip/ala, a mouth with upper/lower lip volumes, ears with concha depth,
       and brow/cheek/jaw planes that survive the 256² AO bake.
       In progress: `tools/npc_parts.py build --part head_proto` displaces the shell (seg 48/rings 26)
-      into sockets, a nose bridge/tip/ala, upper/lower lips and ears; the eyeballs stay separate.
-      Vision-judged (iteration 2): the nose + ear now protrude in profile, but the cranium still
-      reads as a "ball with a nose". Next: flatten the face plane, taper the jaw/chin, widen the
-      nose bridge, and shape the back of the skull before the 1.5 m/1.85 m comparison.
+      into sockets, a nose bridge/tip/ala, upper/lower lips, a chin bump and ears; the eyeballs stay
+      separate. Five vision-judged iterations later (see `docs/3d-model-review.md` §Head prototype):
+      the nose/mouth/chin/ear now read, but the forehead plane, ear helix definition and the
+      jawline-to-neck step still need work before the 1.5 m/1.85 m comparison.
 - [ ] Compare two or three subdivision/loop variants at 1.85 m front/three-quarter/profile and a
       1.5 m portrait. Pick the variant that reads best before changing all 12 characters; keep the
       rejected variants local.