yt-dlp's `max_filesize` only stops a plain HTTP file that announces its size: YouTube's fragmented
formats never meet it — measured on localdev, a 718 MB download ran to the end with 1 MB left and
put its owner four times over the cap. The download now re-reads what is left once its file is made
(after the phone-safe pass) and refuses one larger than that as the owner's refusal; an editor clip,
which nothing checked, is held the same way, as a player clip already was.