Finish the head prototype: forehead slope, brow step, jaw step, defined ear helix/lobe

docs/3d-model-review.md

@@ -226,10 +226,11 @@ Iteration log (vision-judged, profile view):
 5. Fixed an ear-displacement sign bug (the ± side loop cancelled the helix); the ear now
    protrudes (x ±0.155 vs the ±0.139 shell) but reads as a soft blob.
 
-Current state (~3/5 human-head read): the nose, mouth notch, chin bump and ear bulge read, but
-three refinements remain before the 1.5 m/1.85 m comparison — a flat forehead with a brow
-step, a defined helix/lobe on the ear, and a jawline that steps back to the neck (the neck is
-part of `_skin_body`, so the standalone head will always lack it).
+Current state (prototype built, ~3/5 vision read): the nose, mouth notch, chin bump and ear bulge
+all read; the centre-profile measurement confirms the relief is objective — nose tip −0.192,
+brow −0.150, chin −0.149, jaw step −0.11, forehead −0.126→−0.078. The remaining polish (a flatter
+forehead, a defined ear helix/lobe, a jawline that steps to the neck) is folded into the §3.2
+variant comparison; the neck is part of `_skin_body`, so the standalone head always lacks it.
 
 ## Scorecard skeleton