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/AdminUsers.tsx

@@ -232,6 +232,7 @@ function UsersRoles({ me }: { me: Me }) {
                 className={`${SURFACE.card} ${ROW_LAYER} flex items-center gap-2.5 p-2.5`}
               >
                 <Pressable
+                  selectable
                   data-row-open=""
                   onClick={() => setPanelFor(u)}
                   title={t("users.account.open")}