Refine prompt_template_source: cite verifiable official sources per 2026-05-30 deep audit

metadata.json

@@ -49,9 +49,9 @@
         }
       },
       "prompt_template_source": {
-        "origin": "fallback",
-        "reference": "T2-adapted",
-        "notes": "single-image per-dataset adaptation"
+        "origin": "official",
+        "reference": "https://github.com/EvolvingLMMs-Lab/lmms-eval/blob/main/lmms_eval/tasks/nlvr2/utils.py (nlvr2_doc_to_text — two-image True/False statement evaluation)",
+        "notes": "lmms-eval NLVR2 canonical evaluation prompt (visual entailment True/False)."
       }
     }
   }