Refine prompt_template_source for en

metadata.json

@@ -185,8 +185,9 @@
         }
       },
       "prompt_template_source": {
-        "origin": "fallback",
-        "reference": "T3"
+        "origin": "official",
+        "reference": "https://github.com/open-compass/VLMEvalKit/blob/main/vlmeval/dataset/image_mcq.py#L212-L247 (ImageMCQDataset.build_prompt)",
+        "notes": "VLMEvalKit canonical MCQ template (byte-for-byte)"
       }
     }
   }