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.

Tools/ue_character_import.py

@@ -48,14 +48,14 @@ def import_texture_and_material():
     # Interchange 5.8 does not create material/texture assets for skeletal
     # FBX imports; finish the baked-material chain explicitly.
     task = unreal.AssetImportTask()
-    task.filename = "/tmp/gigline/T_Skin_Diffuse.png"
+    task.filename = "/tmp/gigline/T_Character_Diffuse.png"
     task.destination_path = DEST
     task.automated = True
     task.save = True
     task.replace_existing = True
     unreal.AssetToolsHelpers.get_asset_tools().import_asset_tasks([task])
 
-    tex = unreal.EditorAssetLibrary.load_asset(f"{DEST}/T_Skin_Diffuse")
+    tex = unreal.EditorAssetLibrary.load_asset(f"{DEST}/T_Character_Diffuse")
     log(f"texture: {tex.get_class().get_name() if tex else 'MISSING'}")
 
     mat_path = f"{DEST}/M_Character_Export"