Post-download truth for DESIGN.md §5.6: resolution, codec, HDR with the Dolby Vision profile as a number, per-track audio language plus the title and handler_name strings §5.2 needs, subtitles, duration and size. Also picks the feature file out of a multi-file torrent — largest video file, checked against the expected runtime so an extras reel does not get imported as the film. The fixture clips are generated by scripts/make-probe-fixtures.sh. The two Dolby Vision ones splice a dvcC/dvvC box into a real HEVC clip, since x265 will not encode DV without an RPU. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>