- Detect VP9-alpha WebM support once at load; iOS Safari falls back to <img>
- addGhost prefers data.webm via THREE.VideoTexture (browser-decoded, no
per-frame needsUpdate pump) when supported
- On video error, gracefully swap the billboard to the GIF/image texture
- Pause + release ghost <video> elements on capture and on hunt teardown to
avoid leaking decoders