Drop the iOS-grouped rounded card in MediaBrowserView's section
container for top/bottom dividers on macOS, force .buttonStyle(.plain)
on directory NavigationLinks to avoid default link tinting, and
shrink MediaFileRow's icon frame on macOS. iOS and tvOS unchanged.
Playable files in the media source browser now honor tvOSVideoTapAction
on tvOS and thumbnailTapAction/textAreaTapAction on iOS/macOS, matching
other video lists. When openInfo navigates to VideoInfoView, playback
routes through QueueManager.playFromMediaBrowser so stream and caption
resolution keep working for Samba/WebDAV files.
On tvOS, ContentUnavailableView inside a Group doesn't expand to fill
available space — it sizes to content and aligns top-leading. Add
.frame(maxWidth: .infinity, maxHeight: .infinity) to all instances
so they center correctly in their parent containers.
