- facade: oakengine_sequence_set_workarea_undoable (enable+range as one
undo record); marker add/remove/list already existed and are now
covered by it_timeline (10 new tests: markers, workarea, cross-track)
- fixes: stubs workarea_get honored NULL out-params (is_enabled always
failed); export tasks honor custom ranges (export_params_pod dropped
them; oaktask EncodingParams carries has_custom_range)
- app: markers on the ruler (gpui diamond markers), menu
sequence-add/remove marker, set/clear work area (selected-clip bounds
or playhead+1), ruler drag previews live and commits one undoable
record (C++ ruler semantics); export uses the work area when enabled
- cross-track clip moves were already wired; now covered end to end
Mike-Solar
92daff1a83