Rubber-band selection over the projected yuvDragSelectItem children.
Two rules keep it from hijacking ordinary clicks:
a primary-button press that starts inside an interactive element (a tile’s actions-menu button, a link, …) is ignored entirely — see {@link INTERACTIVE_ELEMENT_SELECTOR};
the selection rectangle only comes into existence once the pointer has travelled {@link DRAG_SELECT_THRESHOLD_PX}; below that a press is a click, and no dragSelectChange / dragSelect is emitted.
