Document MPFB full-body NPC prototype status and seams

MEMORY.md

@@ -27,6 +27,18 @@ canonical implemented-features list in `docs/development-status.md`.
   neck/shoulders (shoulder root z 1.345, chest 0.158, neck 0.060/0.054) and its skin
   decimate dropped to 0.21. The local renders are in
   `tmp/npc-parts/prototype_mh/renders/`.
+- **MPFB full-body prototype (2026-11-04):** the current body candidate is the local MPFB 2.0.18
+  pipeline at `tmp/npc-research/build_mpfb_npc.py` (dev-only; no `.mhclo` clothing installed).
+  It creates a macro-driven human, bakes targets, adds the `game_engine` rig, captures arm
+  points/weights, removes the rig, applies the helper MASK, scales to 1.81 m, retargets the A-pose
+  arms to the contract wrist, cuts the neck at 1.505, decimates, bisects the clothing boundaries,
+  paints the five slots, adds a short neck flare, project hands, rounded shoes and cuffs, the
+  accepted head and the 14-bone contract armature. Current output: **15,917 tris / 9,543 raw verts /
+  1.811 m / 14 bones / 10 materials**; `inspect` clean and feet grounded. **Not accepted yet:** the
+  neckline reads as a short collar, the 2k-tri body budget leaves boxy/finned outer thighs, the
+  shoes are blocky, and torso/hip/arm seam gaps appear when the body target is raised. The prototype
+  uses flat slot colours because the one-shot MPFB UV unwrap does not match the per-slot NPC
+  atlases. Renders: `tmp/npc-parts/mpfb_proto/renders/`; body-only: `body_only.glb`.
 - **Project agent skills (2026-11-03):** two tracked skills live in `.agents/skills/`:
   `gig-line-blender-asset-contract` and `gig-line-release-qa`. They are guidance only,
   add no runtime dependency and are referenced from `tools/README.md`. The third-party
@@ -128,6 +140,14 @@ canonical implemented-features list in `docs/development-status.md`.
   (dark tangent patches) — hair skips the normal map. Generate the cap before deleting
   the hidden scalp, or the cap inherits the hole. The flatpak sandbox cannot read `/tmp`;
   helper scripts must live under `$PWD`.
+- MPFB gotchas: call `TargetService.bake_targets(body)` before any decimate (shape-key
+  modifier error); add the built-in rig and capture arm weights before applying the MASK
+  modifier, or `build_basemesh_position_info` divides by zero on an emptied bone group;
+  decimate before bisecting the clothing loops, or the decimator collapses the bisect
+  into a sawtooth. Clear custom split normals after joining (imported MPFB normals leave
+  flat-shaded thigh facets). Imported GLBs may include helper `Cube`/`Icosphere` meshes at
+  ±1.0, so select `npc_base` explicitly. Delete the MPFB hands by hand/finger vertex-group
+  weights, not only by `|x|`, or leftover fingers become pants-coloured fins.
 - Image models have per-model size floors/caps (Seedream needs 1920+; `GEN_SIZE=2048`, do not
   lower; gpt-5-image-mini caps lower). `generate_image` applies model-specific sizing; concept
   generation defaults to `--request-size 1536`.