PLN added quand_on_decolle under a new ## SOUNDCHECK heading mid-session. The
gate caught both downstream consequences without being asked:

  setlist vs backlog  FAIL -> the .txt was 14, backlog.md was 15
  preload covers set  FAIL -> 'airports' would have been read from DISK on
                              first play, i.e. crackle, on the soundcheck track

That is the #120 failure mode caught BEFORE the venue instead of at it, and it
is the second time in two days the backlog->setlist->preload pipe has earned
itself. gig-up: GO, 10/10 cold.

preload.scd takes effect at the next SuperDirt boot — NOT applied live, since
scsynth is up and restarting it costs ~15s of silence.