fix: close start menu popover on repeated click (#2784)

When the Start button is clicked while the popover is already open,
close it instead of doing nothing. This fixes the toggle behavior
on Android Chrome where the menu stays open on repeated taps.

The `.popover-launcher` removal triggers the UIPopover remove event
handler which automatically cleans up the `has-open-popover` class.

Fixes #1681

src/gui/src/UI/UITaskbar.js

@@ -90,6 +90,7 @@ async function UITaskbar (options) {
             // skip if popover already open
             if ( $(item).hasClass('has-open-popover') )
             {
+                $('.popover-launcher').remove();
                 return;
             }
 
@@ -759,4 +760,4 @@ $(document).ready(function () {
     });
 });
 
-export default UITaskbar;
+export default UITaskbar;