Four kenBurns motions chained with crossfade transitions, plus a button that
calls movie.render() from code — the same path the Controller's download button takes,
but here you choose the format and watch the progress event stream.
kenBurns({ asset, motion, ... }) — returns a SequenceSpec ready to drop into sequences[]still, scale (focal-point zoom), rotation, position (pan)movie.render({ format }) returns a Blob; supports 'mp4' / 'webm' / 'mov'movie.on('progress', e => ...)