USAGE:
  sediment export diff-sft [-h] --out OUT [--recipe {sft_curated,sft_verified}]
                           [--from FROM_BUNDLE]

  diff_sft.jsonl — per-commit, per-file training rows

OPTIONS:
  -h, --help            show this help message and exit
  --out OUT             output directory
  --recipe {sft_curated,sft_verified}
                        SFT evidence recipe (default: sft_curated; sft_verified
                        requires opt-in)
  --from FROM_BUNDLE    validated derived bundle directory
