fix(chat): prevent stuck drop overlay when dragging outside window in firefox (open-webui#21664)

Author: silentoplayz

src/lib/components/chat/MessageInput.svelte

@@ -797,7 +797,10 @@
 		}
 	};
 
-	const onDragLeave = () => {
+	const onDragLeave = (e) => {
+		if (e.currentTarget.contains(e.relatedTarget)) {
+			return;
+		}
 		dragged = false;
 	};