Optionalcanvas_Optionalcanvas_Optionalframe_Optionalloop_Playback jumps back to the work area's start (or 0) when it reaches the end. Missing = false.
Optionalstacking_2 = visual tracks share one stacking order and text is sorted with them. Missing = the old rule (orders counted per type, text always on top); such a project is renumbered once when it is opened (see stacking-migration.ts).
OptionalsurfaceWhich surface owns this project. Absent on classic video-editor projects
(they predate this field and never set it); 'orator' on projects created
by Orator. Orator only ever opens its own projects, so the editor's media
never bleeds into the Orator library and vice-versa.
Optionalwork_The slice of the timeline being worked on; playback and export can limit to it. Missing = whole timeline.
Top-level container. One project = one editing session.