ChatDropZone

Wrap the whole chat so files dropped anywhere on it are taken, not only on the composer. While files are dragged over it, an overlay says labels.drop (and labels.hint when set) and screen readers hear it once. Moving between child elements does not flicker the overlay, and dragging text or links is ignored. Pass onFiles, usually onDrop of useFileIntake, so the same accept, maxFiles and maxFileSize apply to picked, pasted and dropped files; or give the zone its own policy and onReject. The overlay already marks the drop, so do not also pass attachments.isDragOver to the composer inside it; the function form of children gets isDragOver for layouts that draw their own highlight instead of the overlay. Dropping is never the only way in: keep the attach button. The kit does not upload; that stays with the host.