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/api/plex.ts

@@ -49,6 +49,8 @@ export interface PlexCard {
   status?: string; // new | watched | hidden
   position_seconds?: number;
   season_count?: number | null; // show
+  // show: an unwatched episode holds a resume point (Continue resumes it, Restart replays it)
+  resumable?: boolean;
   season_number?: number | null; // episode
   episode_number?: number | null; // episode
   show_title?: string | null; // episode (in a mixed playlist)
@@ -626,18 +628,20 @@ export const plexApi = {
     if (filters) appendPlexFilters(u, filters);
     return req(`/api/plex/discover?${u.toString()}`);
   },
-  // A fresh random sample for the Surprise-me rail — a new draw every call (the ↻ refetch), narrowed by
-  // the active filters like the other rails. `exclude` is the previous draw: dealt last, not first.
+  // A fresh random sample for the Surprise-me rail — a new draw every call (the ↻), narrowed by the
+  // active filters like the other rails. `exclude` is the previous draw: dealt last, not first. `keep`
+  // asks for no draw at all: those titles again, in that order, with their watch state as it is now.
   plexSurprise: (
     scope: string,
     limit?: number,
     filters?: PlexFilters,
     lang?: string,
-    exclude: string[] = [],
+    { exclude = [], keep = [] }: { exclude?: string[]; keep?: string[] } = {},
   ): Promise<{ scope: string; items: PlexCard[] }> => {
     const u = new URLSearchParams({ scope });
     if (limit) u.set("limit", String(limit));
     for (const id of exclude) u.append("exclude", id);
+    for (const id of keep) u.append("keep", id);
     if (lang === "hu") u.set("lang", "hu");
     if (filters) appendPlexFilters(u, filters);
     return req(`/api/plex/surprise?${u.toString()}`);

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.

frontend/src/lib/queryKeys.test.ts

@@ -89,12 +89,13 @@ describe("qk — variadic composite plex keys", () => {
       FILTERS,
     ]);
     expect(qk.plexSurprise("movie", "hu", FILTERS)).toEqual([
-      "plex-surprise",
+      "plex-discover",
+      "surprise",
       "movie",
       "hu",
       FILTERS,
     ]);
-    // A bare call stays a prefix for the reshuffle/watched-toggle invalidations.
-    expect(qk.plexSurprise()).toEqual(["plex-surprise"]);
+    // Under the discover root: whatever refreshes the rails refreshes the draw's cards too.
+    expect(qk.plexSurprise()).toEqual(["plex-discover", "surprise"]);
   });
 });

frontend/src/lib/queryKeys.ts

@@ -123,10 +123,11 @@ export const qk = {
   // refetches it alone.
   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). The ↻ reshuffle is the
-  // query's own refetch, and nothing invalidates this key — deliberately: a watched toggle flips the
-  // card in place (and reverts it on a failure) rather than reshuffle the rail under the viewer.
-  plexSurprise: (...rest: unknown[]) => ["plex-surprise", ...rest],
+  // filter narrows against the language-specific genre column, like the grid). UNDER the discover root,
+  // so whatever refreshes the rails (a watched toggle, a player closing) refreshes this one too: its
+  // refetch reads the same draw again (`keep`), and only the ↻ deals a new one. As a sibling root the
+  // draw's cards kept the watch state they were drawn with.
+  plexSurprise: (...rest: unknown[]) => ["plex-discover", "surprise", ...rest],
   plexSuggest: (...rest: unknown[]) => ["plex-suggest", ...rest],
   // Optional trailing `lang`: a language switch remounts the detail with a new key so HU/EN
   // metadata is cached separately. Omitting it (e.g. for a prefix invalidation) still matches both.