Add validated Countix compatibility QA subset and invalid-row report

subsets/countix_compat_summary.json

@@ -10,8 +10,13 @@
   "files": {
     "manifest_tsv": "subsets/countix_compat_all.tsv",
     "video_ids_tsv": "subsets/countix_compat_video_ids.tsv",
-    "qa_tsv": "subsets/countix_compat_qa.tsv"
+    "qa_tsv": "subsets/countix_compat_qa.tsv",
+    "qa_valid_tsv": "subsets/countix_compat_qa_valid.tsv",
+    "qa_invalid_tsv": "subsets/countix_compat_qa_invalid.tsv"
   },
   "qa_rows": 1041,
-  "qa_missing_target_rows": 1
+  "qa_missing_target_rows": 1,
+  "qa_valid_rows": 1040,
+  "qa_invalid_rows": 1,
+  "validation_rule": "valid row requires non-empty video_id/split/count/question/answer/lance_uri and video_id exists in referenced Lance split"
 }