Render via a native SwiftUI List on iOS (NSTableView stays on macOS), behind the
same API. AppKit-only paths (NSTableView coordinator, pasteboard/NSDraggingSession
drag) are guarded for macOS. Adds a cross-platform onRowDragURL modifier driving
.draggable on iOS for row drag-and-drop.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>