Sync with Deployed to… opened the comparison in its own native window on desktop,
but the default-server item, which the context menu shows by the server's name
(and as the only entry when one server is configured), still called the in-page
dialog, so the comparison was confined to the project window. Both actions now
share the same opener: a native window on desktop with a notification when it
can't open, the in-page dialog in the browser build.
Fixes#1459