Fix the prototype crotch material and loosen the shirt

TODO.md

@@ -203,9 +203,10 @@ owner reviews the silhouette and a production integration decision is recorded.
       apply the helper MASK, scale to 1.81 m, retarget the A-pose arms to the contract wrist
       (`x=±0.27`, `z=0.78`), cut the neck at 1.505, decimate, bisect the clothing boundaries, paint
       the five slots, add a short neck flare, project hands, rounded shoe shells, cuffs, the
-      accepted head and the 14-bone armature. Current output: **15,317 tris / 13,507 glTF verts /
-      13,513 seam-split verts / 1.810 m / 14 bones / 10 materials**; `inspect` clean, feet grounded.
-      The torso is inflated radially by 8% between z 0.84 and 1.40 so the shirt is less skin-tight.
+      accepted head and the 14-bone armature. Current output: **15,317 tris / 13,690 glTF verts /
+      13,702 seam-split verts / 1.810 m / 14 bones / 10 materials**; `inspect` clean, feet grounded.
+      The torso is inflated radially by 12% through z 0.72–1.40 (tapering out at the collar) so the
+      shirt reads as fabric rather than body paint.
 - [x] Replace the spiky decimated MPFB hands with the project palm/finger primitives, straighten the
       splayed MPFB feet so the shoes point forward, and use rounded shoe shells + cuffs instead of
       flat blocks. Use flat slot colours in the prototype because the one-shot MPFB UV unwrap does
@@ -228,11 +229,20 @@ owner reviews the silhouette and a production integration decision is recorded.
       for triangle budget after they proved too small to read.
 - [x] Reject the untucked shirt-hem band: both the 0.09 m and 0.12 m cloth cylinders read as a
       hanging white flap at the crotch. The V hem needs a proper clothing shell, not a band.
-- [ ] Owner reviews the updated MPFB body renders (`tmp/npc-parts/mpfb_proto/renders74/`).
-      Remaining known defects: white shirt hem still forms a V at the crotch, the shirt is only
-      partly loosened by the 8% torso inflation, and the 2k-tri body budget leaves some angular
-      thigh facets. A shirt shell is the proper fix for the first two; these are polish, not
-      blockers for the body direction.
+- [x] Fix the neck material rule: the `radius < 0.08` skin test had no Z floor, so it painted a
+      skin patch at the crotch. It is now guarded to `z > 1.35`; the crotch stays pants.
+- [x] Reject three cheap hem fixes: lowering the shirt to z 0.80 turns it into a unitard; tilting
+      the hem up at the front reads as high-cut swimwear; a 13% hem flare reads as a peplum.
+      The remaining V is the dark crotch hollow under a body-painted shirt, not a slot bug.
+- [ ] Owner reviews the updated MPFB body renders (`tmp/npc-parts/mpfb_proto/renders82/`).
+      Remaining known defects: the crotch hollow still reads as a V under the shirt hem, the
+      shirt is only partly loosened by the 12% torso inflation, and the 2k-tri body budget leaves
+      some angular thigh facets. A separate loose shirt shell is the proper fix for the first
+      two; these are polish, not blockers for the body direction.
+- [ ] Build a separate loose shirt shell (open hem, shaped to the hips) instead of body-painted
+      cloth. It must fit in the 683 spare triangles or come with a head/body triangle rebalance.
+- [ ] Rebalance the triangle budget before rollout: 683 spare is below the ~1,200 the firefighter
+      and hoodie variants need. Protect the head budget first; do not lower the accepted face.
 - [ ] Fix the low-budget seams before any rollout: weld the torso/hip/arm components after the
       bisects, protect the hip/knee loops during decimation (or rebalance head/body triangles).
 - [ ] Record the production integration decision: either bake the approved MPFB body to a committed