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/PlexBrowse.tsx

@@ -583,6 +583,7 @@ export default function PlexBrowse() {
             >
               {/* The photo + name open the actor's filmography page; the ✕ removes the filter. */}
               <Pressable
+                selectable
                 onClick={() => onOpenPerson(p.name)}
                 title={t("plex.info.viewPerson", { name: p.name })}
                 className="group/person flex min-w-0 items-center gap-2.5 rounded-lg"