` elements — drag-and-drop + file
* input, per-file progress bars, and success/failed states. Injected by
* `collectScripts` only on pages that contain `data-uploader` (same mechanism as
* `validate.js`). Self-contained: it injects its own themed stylesheet (using
* `--wire-*` tokens) and posts each file via XHR so upload progress is live.
*
* Markup it enhances (also a valid no-JS `