[Linuxuser67]

Follows the audit of the yt-dlp surface:

• remove() now drops staging_dir(id) for video rows via the guarded clean_staging helper (previously prod-unused). Pause/cancel keep staging for resume; live rows are exempt since their worker was only signaled and finalizes itself. delete_download is covered through remove().
• Both yt-dlp page-URL argv sites (fetch_video_page, run_hls_ytdlp) now end options with -- before the URL. ffmpeg -i sites need none (flag values).
• select_hls_format sorts candidates ascending, so the height cap genuinely picks smallest-at-or-above regardless of extractor order (serves the VOD preset and the live path alike).

Tests: remove() cleans video staging, exempts live rows, leaves plain rows alone; HLS selection ignores extractor order (negative-controlled: fails without the sort). 202 passing, clippy clean.