fix(gate): green the frontend gate at HEAD

- PlexPersonView.dom.test.tsx: variadic vi.fn mock for plexSetState so the
  spread call typechecks (TS2556 — zero-arg mock couldn't take ...args).
- plexSearch.ts: drop the unused `export` on PLEX_SEARCH_FIELDS (module-local
  only; knip flagged it as an unused export).

tsc / knip / lint all green; ruff clean.

frontend/src/components/PlexPersonView.dom.test.tsx

@@ -15,7 +15,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 });
 
 const plexPerson = vi.fn();
-const plexSetState = vi.fn(() => Promise.resolve());
+const plexSetState = vi.fn((..._a: unknown[]) => Promise.resolve());
 vi.mock("../lib/api", () => ({
   api: {
     plexPerson: (...a: unknown[]) => plexPerson(...a),

frontend/src/lib/plexSearch.ts

@@ -4,7 +4,7 @@
 
 export type PlexSearchField = "all" | "title" | "people" | "summary" | "episode";
 
-export const PLEX_SEARCH_FIELDS: PlexSearchField[] = [
+const PLEX_SEARCH_FIELDS: PlexSearchField[] = [
   "all",
   "title",
   "people",