Populate prompt_template_source for all subsets per 2026-05-30 audit

metadata.json

@@ -57,6 +57,10 @@
             "cc_test": "https://huggingface.co/datasets/lmms-lab/MMBench"
           }
         }
+      },
+      "prompt_template_source": {
+        "origin": "fallback",
+        "reference": "T3"
       }
     },
     "cn": {
@@ -115,6 +119,10 @@
             "cn_test": "https://huggingface.co/datasets/lmms-lab/MMBench"
           }
         }
+      },
+      "prompt_template_source": {
+        "origin": "fallback",
+        "reference": "T3"
       }
     },
     "en": {
@@ -173,6 +181,10 @@
             "en_test": "https://huggingface.co/datasets/lmms-lab/MMBench"
           }
         }
+      },
+      "prompt_template_source": {
+        "origin": "fallback",
+        "reference": "T3"
       }
     }
   }