Fix layout: place 63,941-row parquet at data/ and remove stray root-level parquet

data/train-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:d9ba04ef0ce3f7c22dca6a35a2e7c9c303d8aa8144c0159e5b4aa4c82536b4d9
-size 139969975
+oid sha256:3f80c37ce71c9c104e6fa572c30f077735d425e90987e85416b1780fc009aabd
+size 783127823

train-00000-of-00001.parquet

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:3f80c37ce71c9c104e6fa572c30f077735d425e90987e85416b1780fc009aabd
-size 783127823