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

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Restructure train/: nest shards into chunk subdirs (batch 4/98)

Restructure train/: nest shards into chunk subdirs (batch 3/98)

Restructure train/: nest shards into chunk subdirs (batch 2/98)

Restructure train/: nest shards into chunk subdirs (batch 1/98)

Restructure train/: nest shards into chunk subdirs (batch 1/99)