A queue replace starts playback from the first resolved chunk. If that
chunk's track is is_skipped, or is so short it finishes before the next
chunk resolves, play() found nothing playable and stopped the player --
and the later chunks return None (append mode), so playback never
resumed even though playable tracks were arriving right behind it. The
queue sat stopped with tracks in it. This is exactly the short/skipped
leading-track case the read-ahead is meant to cover.
A pending op now carries a wants_start flag: set when a chunk makes a
track current, cleared only once a start is confirmed (play now returns
whether it handed a track to the player). While set, each arriving chunk
retries the start from the current position -- next_playable_urls
advances past skipped/unplayable heads to the first track that has since
resolved. Once playback takes hold the flag clears, so later chunks only
extend the queue and never restart the playing track, and a user stop
after playback started is respected. An op whose whole resolve yields
nothing playable is dropped and the player stays stopped.
play() returns bool; the now-redundant play_if_some helper is removed.
Documented as architecture/progressive-queueing.md D5. Tests cover the
wants_start lifecycle (set on first current-making chunk, held across
later chunks, cleared on mark_started; never set appending behind a
playing queue).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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