fix(plex): Restart only where an episode has a resume point; the Surprise draw is re-read, not redrawn

Show cards carry resumable (ShowState, from the same rollup) so a part-watched
show whose next episode is untouched offers Play, not a Continue and a Restart
that do the same thing; plexStarted is the one rule for cards and menus. The
Surprise rail's key sits under the discover root: whatever refreshes the rails
re-reads the draw (keep=) with its watch state now, kept past the 5-minute gc,
and only the reshuffle deals. Closing the player refreshes the Discover rails.
A show card's play acts on the last click only, and only where it was made.

frontend/src/lib/plexPlayerHooks.ts

@@ -334,6 +334,8 @@ export function usePlexProgress(opts: {
       finishRef.current = () => {};
       qc.invalidateQueries({ queryKey: qk.plexLibrary() });
       qc.invalidateQueries({ queryKey: qk.plexShow() });
+      // The Discover rails (Continue watching, the Surprise draw's cards) hold watch state too.
+      qc.invalidateQueries({ queryKey: qk.plexDiscover() });
     };
     // absRef/durationRef/videoRef are stable ref objects — listed to satisfy exhaustive-deps without
     // changing when the effect re-runs (id/qc only), matching the original in-component effect.