The double-click that opens the popover lands outside it in the same frame, so the popover
closed as soon as it opened; only a later click elsewhere closes it now. The selected stop
remembers the document, first selected object and proxy it was picked on (Session::selected_stop),
so selecting other art or toggling Fill/Stroke no longer lets Delete or the arrows edit a stop
on a different gradient.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>