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/PlexPlaylistView.tsx

@@ -190,6 +190,7 @@ function EpisodeRow({ ep, ctx, dense }: { ep: PlexCard; ctx: Ctx; dense: boolean
         {ep.episode_number}
       </span>
       <Pressable
+        selectable
         onClick={() => ctx.onPlay(ep.id)}
         data-nav-open
         className="group/thumb flex min-w-0 flex-1 items-center gap-2.5"
@@ -242,6 +243,7 @@ function MovieRow({ item, ctx }: { item: PlexCard; ctx: Ctx }) {
         {...listeners}
       />
       <Pressable
+        selectable
         onClick={() => ctx.onPlay(item.id)}
         data-nav-open
         className="group/thumb flex min-w-0 flex-1 items-center gap-3"
@@ -327,6 +329,7 @@ function ShowGroup({ block, ctx }: { block: ShowBlock; ctx: Ctx }) {
           </Pressable>
         )}
         <Pressable
+          selectable
           onClick={() => ctx.toggleShow(block.showKey)}
           data-nav-open
           className="min-w-0 flex-1"