Replace character assets with glossy anime key art

scripts/validate_assets.py

@@ -70,6 +70,12 @@ def main() -> None:
         fail(f"style reference is missing: {reference}")
     png_dimensions(reference)
 
+    for alternate in assets_doc["style"].get("alternates", []):
+        alternate_reference = ROOT / alternate["reference"]
+        if not alternate_reference.exists():
+            fail(f"alternate style reference is missing: {alternate_reference}")
+        png_dimensions(alternate_reference)
+
     for entry in asset_entries:
         status = entry["status"]
         if status not in {"accepted", "needs_revision", "pending", "rejected"}: