Strip all derived output: the library verdict, the XMP edit-trail
parse, and the IJG quality estimate. The script now collects raw bytes
plus mechanical container decodes only, is fully standalone (no
remove_ai_watermarks import), and resumes interrupted runs. Add GIF,
BMP, and TIFF magic bytes to sniff_format (GIF files in the wild were
reported as unknown). Validated on the full 42k-file corpus: 100%
coverage, zero error records.