Completely removes dnd-kit's useDroppable and collision detection for rack slot targeting. Uses onDragMove + document.elementFromPoint() with data-rack-id / data-u-pos HTML attributes on RackSlot elements to resolve the hovered slot independently of dnd-kit's SortableContext interference. Adds pointer-events-none to ModuleBlock when isDragging so the invisible element doesn't block hit testing. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>