Split perturbations by eval split (msmarco-dev/trec-dl-2019/trec-dl-2020), add TSV format with original+perturbed query text, add data_download scripts for MS MARCO/TREC-DL originals

Add weight-file links and from_pretrained usage snippet

Correct provenance, licensing, and citation details: README.md

Upload PAG checkpoint, document identifiers, and Lost-in-Decoding evaluation artifacts