auto-motion 是做什么的？
Use when the user wants a short, design-led motion graphic where motion is the message: kinetic typography, stat or number count-up, chart/data-viz hit, logo sting, brand lockup, lower-third, callout, social overlay, animated headline/tweet/news item, motion poster, or quick captured-page highlight. Usually under 10s and up to ~30s, with no live-action subject. Can render to MP4 or transparent overlay. Not for longer, multi-scene, or brand-reel pieces (use general-video), topic explainers (facel