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.

.gitignore

@@ -52,6 +52,11 @@ Thumbs.db
 # Blender/Blosm working caches
 /Art/blender/.cache/
 
+# Rendered screenshots for visual review — generated locally, never committed.
+# Keeps only the review README (see AGENTS.md Visual review).
+/Screenshots/*
+!/Screenshots/README.md
+
 # Scratch files
 .tmp-*