The add-to-playlist, download options and queue sheets were declared in
every view that could open them: the root view (twice, mirrored from
coordinator flags), the expanded player, its portrait and floating
panels, the player controls and the video info view.
AppSheet lists the shared sheets, and .appSheetHost() declares them
once. The app root and the expanded player each host them, and every
presented sheet hosts the next level. Views present through the
presentAppSheet environment action, which reaches the nearest host;
code without a view (and the expanded player itself, whose host sits
in its own body) uses PresentationRouter.request, taken by the
top-most host: the player while it is up, the root otherwise.
The mini player's queue and playlist sheets now go through the host,
replacing the isMiniPlayer*SheetPresented flags.
When enabled (the default), share links to YouTube videos point to the
active source's web watch page instead of youtube.com. Invidious serves
its frontend at the API URL; Piped uses its configured frontend URL.
Videos the active source can't serve (PeerTube, extracted sources) and
sources without a web frontend keep their original links.
The toggle lives in Settings > Layout & Navigation > Sharing on iOS and
macOS, and is shown only when an enabled source has a web watch page.
