logic: rename info.task -> info.task_name

The plain-string `info.task` field collides with verifiers' reserved `info['task']` key (used for serialized task-payload routing, which must be a JSON object). Rename to `info.task_name`.

logic/train-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:00a53ec72be341798d83fec10425382db415e292135fae4515ee08cf25458008
-size 16737561
+oid sha256:91be0da16cec15ef67c6ec7e4de1371811344507df15d8a412077ce95dc39f41
+size 16506139