Replace the per-row checkbox + numeric Order table on the blueprint
detail page with a drag-to-reorder list of selected overlays plus a
native <select> for adding more. Removing uses an × button per row;
the option sorted-inserts back into the dropdown alphabetically.
Native HTML5 drag-and-drop, no library, no JS-disabled fallback.
Server contract is unchanged: each list row owns one hidden
<input name="overlay_ids">, DOM order = submission order, and the
existing fallback_position branch in ordered_overlay_ids_from_form
absorbs the now-omitted overlay_position_<id> fields.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
a4e9f6cd26