Add the corrected non-leaking split with per-record source attribution

.gitattributes

@@ -60,3 +60,4 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 *.webm filter=lfs diff=lfs merge=lfs -text
 train.json filter=lfs diff=lfs merge=lfs -text
 combined.json filter=lfs diff=lfs merge=lfs -text
+manifest.jsonl filter=lfs diff=lfs merge=lfs -text

manifest.jsonl

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ec8618c24cf7074a2bb661c89b1b9868bc7135af4fd9247f999ce40a21537696
+size 34487243