- ScenarioPoster: remove bg-black/50 and backdrop-blur-sm so demo
  content is fully visible before playback. The play button circle
  (bg-white/90 + glow + ring) provides sufficient affordance on its own.
- ScenarioPauseOverlay: same treatment, remove bg-black/40.
- DemoViewport: start zoom as null instead of 1 and hide inner content
  with visibility:hidden until the first ResizeObserver measurement.
  Prevents the flash where the demo renders at full 896px width then
  snaps to the correct scaled size.

Made-with: Cursor