fix(e5): deep-review round — combobox Enter, parse_person collision, enrich hardening + coverage

Full-epic /deep-review (11 finders + 12 adversarial verifiers) surfaced no HIGH; every
mechanism finding calibrated to LOW on verification. Fix all 13:

Correctness / reliability:
- Combobox: Enter now commits the VISUALLY highlighted row (highlightIndex ?? activeIndex),
  not the bare keyboard activeIndex — so arrow-then-hover-then-Enter no longer toggles a
  different option than the one painted, and hover-with-no-arrow is no longer a silent no-op.
- parse_person: dedup the known_for pool by (id, media_type), not the bare id — TMDB movie
  and tv id spaces are independent, so a same-id movie+show pair is two distinct credits
  (matches the collision-safe key the rest of the module already uses).
- person-enrich: a per-person in-flight + 60s cooldown guard (people._should_schedule_enrich)
  dedups concurrent opens and rate-limits re-triggering while TMDB is degraded (a transient
  TmdbError leaves the watermark NULL), so bursts can't pile 8s tasks onto the shared threadpool.
- PlexInfo compact()/money(): format with i18n.language (keeping currency USD) instead of a
  hardcoded en/en-US, matching the app's Intl convention.
- delete the dead `plex.filter.add` i18n key (both locales) — the +Add button that used it is gone.

Reuse:
- _continue_watching reuses rollup.agg_subquery(include_resumed=True) + query.apply_show_state_filter
  instead of a third hand-inlined copy of the per-show rollup + in_progress predicate, so the
  Discover rail can't drift from the grid's definition.

Test coverage (the gaps a regression would ship through):
- resolve_library_guids scope-exclusion (a credit in a non-scoped/disabled library is dropped)
  + the []-vs-None distinction; parse_person cross-media-id retention; enrich_person transient
  (NULL watermark) and 404 (stamp) branches; _enrich_person_bg body (fresh session close/rollback,
  None-guard) + the cooldown dedup; continue_watching fully-watched-show exclusion; Combobox
  Enter-commits-highlighted + async/controlled-query mode; PopoverItem aria-checked contract;
  RatingsRow missing-IMDb + imdb==audience branches.

Backend lane 413→420, FE vitest 351→357; all gates green. No migration.

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

@@ -127,6 +127,71 @@ describe("Combobox", () => {
     expect(screen.getByText("plex.filter.moreRefine")).toBeTruthy(); // 10 hidden behind search
   });
 
+  it("Enter commits the pointer-highlighted option, not the arrow-active one", () => {
+    // The visible highlight follows the pointer (hoverIndex); Enter must commit THAT row, not the bare
+    // keyboard activeIndex — otherwise arrow-then-hover-then-Enter toggles a different option than shown.
+    const onChange = vi.fn();
+    wrap(<Combobox label="Genre" options={OPTIONS} selected={[]} onChange={onChange} />);
+    const input = screen.getByRole("combobox");
+    input.focus();
+    fireEvent.focus(input);
+    fireEvent.keyDown(input, { key: "ArrowDown" }); // activeIndex → 0 (Drama)
+    const action = screen
+      .getAllByRole("option", { hidden: true })
+      .find((el) => el.textContent?.includes("Action"))!;
+    fireEvent.mouseMove(action); // hoverIndex → Action (the visibly highlighted row)
+    fireEvent.keyDown(input, { key: "Enter" });
+    expect(onChange).toHaveBeenCalledWith(["Action"]); // the highlighted (hovered) row, not Drama
+  });
+
+  it("Enter commits a hover-highlighted option even with no prior arrow key", () => {
+    const onChange = vi.fn();
+    wrap(<Combobox label="Genre" options={OPTIONS} selected={[]} onChange={onChange} />);
+    const input = screen.getByRole("combobox");
+    input.focus();
+    fireEvent.focus(input);
+    const comedy = screen
+      .getAllByRole("option", { hidden: true })
+      .find((el) => el.textContent?.includes("Comedy"))!;
+    fireEvent.mouseMove(comedy); // highlight via hover, activeIndex still null
+    fireEvent.keyDown(input, { key: "Enter" });
+    expect(onChange).toHaveBeenCalledWith(["Comedy"]); // no longer a silent no-op
+  });
+
+  it("async mode: controlled query + onQueryChange/onOpenChange, no client filter, selectedLabels chip", () => {
+    const onQueryChange = vi.fn();
+    const onOpenChange = vi.fn();
+    const onChange = vi.fn();
+    const serverOpts = [{ value: "id1", label: "Harry Potter", count: 8 }];
+    wrap(
+      <Combobox
+        label="Collection"
+        multiple={false}
+        clientFilter={false}
+        options={serverOpts}
+        selected={["stored-id"]}
+        selectedLabels={{ "stored-id": "Stored Collection" }}
+        query="har"
+        onQueryChange={onQueryChange}
+        onOpenChange={onOpenChange}
+        onChange={onChange}
+      />,
+    );
+    // The selected value's option isn't in the (server-narrowed) list, so its chip uses selectedLabels.
+    expect(screen.getByText("Stored Collection")).toBeTruthy();
+    const input = screen.getByRole("combobox");
+    fireEvent.focus(input);
+    expect(onOpenChange).toHaveBeenCalledWith(true);
+    fireEvent.change(input, { target: { value: "harr" } });
+    expect(onQueryChange).toHaveBeenCalledWith("harr"); // controlled query propagates out
+    // clientFilter=false: the single server option renders verbatim (not re-filtered against "har").
+    const opts = screen.getAllByRole("option", { hidden: true });
+    expect(opts.length).toBe(1);
+    expect(opts[0]?.textContent).toContain("Harry Potter");
+    fireEvent.click(screen.getByText("Harry Potter"));
+    expect(onChange).toHaveBeenCalledWith(["id1"]); // single-select replaces
+  });
+
   it("single-select: picking replaces the value and closes the list", () => {
     const onChange = vi.fn();
     wrap(