Delete declarations that Periphery reports unused on every platform that
compiles them (iOS, macOS, tvOS), including nine views used only by their
own previews. Platform-gated code still used on another platform, device-
only MPV render paths, migration models, CloudKit record names, App
Intents metadata and unused parameters are kept.
The screen read local playlists and nothing else, so selecting an account
moved the subscriptions and the feed but left this list showing the
device's own playlists with no way to tell. It now follows the effective
context: local as before, or the account's list read live out of
RemotePlaylistsCache — never copied into state, because every change to a
server-side playlist goes through that cache and reading it is what makes
a rename or a delete show up.
Rows carry both the account's instance and the account's id, which have
to agree or UnifiedPlaylistDetailView drops ownership and the playlist
loses its edit and delete. Editing refetches first, exactly as the detail
view does: the form saves every field at once, and one started from a row
fetched minutes ago would put that row back over anything changed since.
Deleting from a server asks first; deleting a local playlist stays
unconfirmed as it always was.
Row identity, item mapping and the search filter move into
PlaylistListItem, where they can be tested — the transition id stays
separate from the row identity because it has to match what
PlaylistSource produces for the destination.
Local behaviour is unchanged throughout: the same rows, the same swipe
actions, the same unconfirmed delete, and the same synchronous read on
appear so the empty state never flashes.
