- ytdlp::download() accepts quality: Option<&str>; quality_format()
maps best/1080p/720p/480p/360p to yt-dlp -f format strings
- perform_capture() threads quality through to the downloader
- CaptureBody gains optional quality field; capture_handler validates
it against the allowlist (400 on unknown values) before spawning
- CLI passes None (preserves existing best-quality behaviour)
- Frontend: isVideoSource() mirrors determine_source() exactly —
shows quality picker only for yt-dlp-backed sources, excludes
playlist/channel shorthands and tweet/thread paths
- submitCapture(archiveId, locator, quality) sends quality in POST body
- CSS: .capture-quality styles the inline select to fit the capture row
- Tests: quality_format unit tests in ytdlp.rs; two new route tests
(valid quality accepted, invalid quality rejected with 400)
- Docs: video quality section added under Supported Platforms
