RealEngine::set_track_height held the project graph lock while calling
graphops::set_track_height, which locks the same mutex — an instant
same-thread deadlock with any sequence open (sampled live: main thread
in nudge_track_height -> set_track_height -> Mutex::lock, no other
lock-holder thread). Collect the track ids under the lock, drop it,
then apply the heights.
Also:
- Regression test set_track_height_does_not_self_deadlock.
- save_load_roundtrips_a_timeline_clip: real footage through the OVE
serializer (also the fixture generator for viewer debugging).
Mike-Solar
53dbaba8fe