- new facade API: video params ex (dimensions/rate/par/interlacing/
preview format/divider), audio params, preview divider, and
undoable-flagged setters mirroring the dialog's dual undo/no-undo
modes; label setting gains node_set_label_ex
- the dialog's own SequenceParamCommand is gone; accept now issues
facade calls (per-field commands, unchanged fields skipped)
- preset system stays UI-side by design: its flat XML schema never
touches engine objects
- the auto-cache checkbox maps to the engine's existing stub (no undo
noise)