wl_backend: reset cursor to left_ptr on ungrab — same logic as dock/clip drags

src/backend/wayland/wl_backend.c

@@ -6317,6 +6317,8 @@ static void wl_pointer_ungrab(unsigned long timestamp)
     if (wl_state.grab_type == 3) {
         wl_state.grab_type = 0;
         wl_state.grab_view = NULL;
+        /* Reset cursor to default arrow when WM policy grab ends. */
+        wl_set_cursor_image("left_ptr");
     }
 }