When all playlists/subscriptions were imported, every row collapsed to a
non-focusable checkmark and the Add All toolbar item disappeared, leaving
the view with no focusable element. The Menu button then closed the app
instead of popping the navigation stack.
Wrap the import destinations in TVSidebarDetailContainer for visual
consistency and add a Done toolbar item (cancellationAction) that is
always present on tvOS, reachable from any list row via swipe-up.
Give TVSidebarDetailContainer an optional bottom action slot and use it to
show the Add Source button beside the sources list on tvOS. Switch the
Settings > Sources list from a focus-capturing List to the same
ScrollView+LazyVStack layout MediaSourcesView already uses, drop
.buttonStyle(.card) so row icons no longer clip, and bump the row
icon-to-title spacing to 24pt. Replace the sheet-based Add/Edit flow in
MediaSourcesView with navigationDestinations wrapped in the sidebar
container, and decorate each Add Source form (WebDAV, SMB, remote server,
PeerTube browse) with its own sidebar icon and title.
