backfill: add v2 manifest fields (additive, idempotent)

Re-narrate with gpt-5.4-pro

backfill: fix missing deliverable_files

backfill: add instruction, reference_file_urls, deliverable_files to task_results

Add self_report.json (backfill from report_data.json)

Update dataset with experiment results

Upload folder using huggingface_hub

initial commit