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/ui/Pressable.tsx

@@ -18,6 +18,8 @@ export const Pressable = forwardRef<
     align?: "left" | "center";
     /** Working: unavailable and announced as busy. */
     busy?: boolean;
+    /** Its text is a title or a name: it stays selectable (see FocusSafeButton). */
+    selectable?: boolean;
   }
 >(function Pressable({ type, layer = false, align = "left", className, ...rest }, ref) {
   return (