Restructure train/: nest shards into chunk subdirs (batch 97/98)

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Restructure train/: nest shards into chunk subdirs (batch 20/98)

Restructure train/: nest shards into chunk subdirs (batch 19/98)

Restructure train/: nest shards into chunk subdirs (batch 18/98)

Restructure train/: nest shards into chunk subdirs (batch 17/98)

Restructure train/: nest shards into chunk subdirs (batch 16/98)