In Classify & Copy mode the left tree now lists each folder's files as
draggable rows (with a classification state dot), and folder rows are
draggable for a group-drag of the whole subtree. Target-tree nodes are drop
zones: a tracking folder (any node) or a transmittal bin; dropping assigns the
dragged source key(s) along that axis via classify.place().
- dnd.js: drag-payload bus (keys held in a module var since dataTransfer can't
be read during dragover; carries a marker for the copy cursor).
- tree.js: createFileElement + group-drag dragstart; classify-mode file rows.
- target-tree.js: setupDropZone with dragover highlight + drop assignment
(tracking = any node, transmittal = bins only).
- app.js: source tree re-renders on classify state change.
- 2 DnD drop-handler tests (14 total green).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
