character: idle standing pose and warm skin, not the grey mannequin

- mpfb_character_export.py: new --pose idle folds the A/T-bind arms down to
  a relaxed standing rest pose (baked via pose.armature_apply before export);
  new make_diffuse synthesizes a warm skin-tone diffuse with a darker
  shorts-suggestive band, replacing the Cycles v2-skin bake that came out
  black and was slow at 1024^2.
- write_png now encodes from img.pixels via numpy (fast) because img.save()
  writes black for an in-memory image.
- Re-exported idle character, re-imported to /Game/Test/Character (138 bones,
  warm M_Character_Export/T_Character_Diffuse); removed stale T_Skin_Diffuse.
- Untracked the review PNGs again: the Screenshots/ gitignore rule had been
  dropped and the parallel session had committed the PNGs, against the
  AGENTS.md 'never commit the PNGs' rule. Restored the ignore rule; only
  Screenshots/README.md stays tracked.
- README/roadmap/memory updated; review-01-character re-pended for approval.

Screenshots/README.md

@@ -33,11 +33,11 @@ add new shots there and delete retired ones from this folder.
 
 Character and both cubes on the 160 m floor, camera 7 m up looking north-east. Reads the whole review layout at once.
 
-## review-01-character.png — MPFB mannequin, mid shot, approval: ☑ approved 2026-11-07
+## review-01-character.png — MPFB mannequin, idle pose + warm skin, approval: ☐ pending (regenerated 2026-11-07)
 
-![MPFB mannequin, mid shot](review-01-character.png)
+![MPFB mannequin, idle pose + warm skin](review-01-character.png)
 
-The imported MPFB character at eye height from the south. Check the feet meet the plane: the contact shadow joins the soles.
+The imported MPFB character at eye height from the south, in a relaxed standing idle pose (arms down, not A-pose) with a warm skin-tone diffuse instead of the grey mannequin. Check the feet meet the plane: the contact shadow joins the soles.
 
 ## review-02-scale-cubes.png — Scale cubes, approval: ☑ approved 2026-11-07