The dropdown panel only closed through its own X button. Escape already
dismissed it, so the missing pointer equivalent left the panel stuck open
over the page after a stray tap.
Close it on any click landing outside the panel and outside the labels that
toggle it. Both early returns are load-bearing. A label forwards a synthetic
click to its checkbox, so without skipping the input the menu closes in the
same gesture that opened it. And without skipping the opener, opening then
closing with the hamburger leaves the panel open, because this handler and
the label's default action cancel each other out.
The fullscreen panel needs no special case. It covers the viewport, so
every click lands inside it and the handler stays inert.
Metalhearf