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/playlistColumns.tsx

@@ -74,6 +74,7 @@ export function playlistColumns({
             </span>
           </Pressable>
           <Pressable
+            selectable
             onClick={() => onPlay(v)}
             // The row's "open" element: Enter on a keyboard-walked row (lib/listNav) plays it.
             data-nav-open=""