Replaces the parallel httpx download with mpv's stream-record per-file
option. When play_file receives an HTTP URL, it passes stream_record
pointing at a .part temp file alongside the URL. mpv writes the incoming
network stream to disk as it decodes, so a single HTTP connection serves
both playback and cache population.
On clean EOF the .part is promoted to the real cache path via os.replace.
Seeks invalidate the recording (mpv may skip byte ranges), so
_seeked_during_record flags it for discard. stop() and rapid-click
cleanup also discard incomplete .part files.
At this commit both pipelines are active — _load still runs the httpx
download in parallel. Whichever finishes second wins os.replace. The
next commit removes the httpx path.
pax
a01ac34944