fix(plex): a reshuffle survives a refresh landing mid-deal; the ↻ spins for a deal only

The ↻ intent was spent as its fetch set out, so a watched toggle's resync cancelling that fetch re-ran it as a re-read of the old draw. It now lasts until the latest deal answers. The button spun on every re-read of the same titles; it now follows the deal. Comments that said the Surprise draw is never refetched are brought in line.

frontend/src/lib/queryKeys.ts

@@ -118,9 +118,8 @@ export const qk = {
   plex: () => ["plex"] as const,
   plexWatchLink: () => ["plex-watch-link"] as const,
   plexLibrary: (...rest: unknown[]) => ["plex-library", ...rest],
-  // Discover surface: the rail payload keyed by scope+lang; `plexDiscover()` (no args) matches
-  // both for a prefix invalidation after a watched-toggle. Surprise is its own key so the ↻ reshuffle
-  // refetches it alone.
+  // Discover surface: the rail payload keyed by scope+lang; `plexDiscover()` (no args) matches it and
+  // the Surprise draw below for a prefix invalidation after a watched-toggle.
   plexDiscover: (...rest: unknown[]) => ["plex-discover", ...rest],
   // Variadic like plexDiscover so it can key by scope + lang + the active filters (lang because a genre
   // filter narrows against the language-specific genre column, like the grid). UNDER the discover root,