Playlist reordering existed but was broken whenever a track was playing:
the ~400ms progress re-render replaced the dragged node and cancelled the
browser drag instantly. renderPlaylist now defers rebuilds until dragend,
drops show an insertion marker (top half = before, bottom half = after),
and internal drags no longer trigger the file-drop overlay.
Scene editor: elements get a drag grip; since the list is always shown
time-sorted, dropping an element between two others moves its appearance
time between theirs (before the first = half its time, after the last =
+5s). Grip-armed dragging keeps the sliders inside the cards working.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
