feat(design): titles in click surfaces stay selectable (E28 S3e4b)

A button whose text is a title or a name is now `selectable` (FocusSafeButton,
under Pressable and Button): Chrome selects inside a button once it is
user-select: text (measured), and the click that ends a selection, or a press
dragged past the slop, opens nothing. 23 surfaces carry it (cards, rows, people,
channels, playlists, users, views, messages, log lines, description links); the
Plex caption div gets the same guard. A contract test pins every plain Pressable
with its reason, so a new one has to choose.

frontend/src/components/Home.tsx

@@ -283,6 +283,7 @@ function ShelfTile({
       : t("home.shelf.itemCount", { count: count ?? 0 });
   return (
     <Pressable
+      selectable
       onClick={() => card.next && onPlay(card)}
       {...menuProps?.(card)}
       {...(navIndex !== undefined && navItemAttrs(navIndex))}