Upload Element Previews

1. Identify the Element slug. Ask if it is ambiguous.
2. Choose the source:
   • Use render for fresh files in .element-previews.
   • Use submission for committed files in static/elements.
3. Upload the previews:

cd packages/docs
bun run upload-element-preview \
  --element=<category>/<slug> \
  --source=<render|submission>

To refresh an already-published preview, add --overwrite. The uploader accepts it only when the Element definition already uses the exact expected https://remotion.media/elements/... PNG and MP4 URLs.

4. For a new preview, replace image, posterUrl, and videoUrl with the printed remotion.media URLs. An overwritten preview keeps its existing URLs.
5. If using submission, delete the local review assets. If using render, leave .element-previews uncommitted.
6. Commit and push when the work belongs on a branch.