test(i18n): a language test unmounts its reader before switching the language back

useTags reset the language in a finally while its hook was still mounted;
the switch scheduled a render, and in a loaded gate run it landed after
the jsdom environment was torn down ('window is not defined', two
unhandled errors). auditColumns and comfortPin had the same shape.

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

@@ -4,12 +4,17 @@
 // "log_level = DEBUG", "Background sync paused") reads in the reader's language, rebuilt from the row's
 // data through the REAL catalog. A row whose summary is data (an e-mail, a URL) keeps it.
 import { afterEach, describe, expect, it } from "vitest";
-import { fireEvent, render } from "@testing-library/react";
+import { cleanup, fireEvent, render } from "@testing-library/react";
 import i18n, { setLanguage } from "../i18n";
 import type { AuditRow } from "../lib/api";
 import { auditColumns } from "./auditColumns";
 
-afterEach(() => setLanguage("en"));
+// Unmount BEFORE the language goes back: a mounted reader re-renders on the switch, and under a loaded
+// run that render landed after the test environment was gone ("window is not defined", E31 S5).
+afterEach(() => {
+  cleanup();
+  setLanguage("en");
+});
 
 const row = (over: Partial<AuditRow>): AuditRow => ({
   id: 1,

frontend/src/components/comfortPin.langSwitch.dom.test.tsx

@@ -6,13 +6,16 @@
 // i18n (the key-echo mock does not re-render on a switch, which is the very thing under test).
 import { describe, it, expect, afterEach, vi } from "vitest";
 import type { ReactNode } from "react";
-import { renderHook, act, waitFor } from "@testing-library/react";
+import { renderHook, act, waitFor, cleanup } from "@testing-library/react";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { setLanguage } from "../i18n";
 import { api } from "../lib/api";
 import { useComfortPin } from "./comfortPin";
 
+// Unmount BEFORE the language goes back: a mounted reader re-renders on the switch, and under a loaded
+// run that render landed after the test environment was gone ("window is not defined", E31 S5).
 afterEach(() => {
+  cleanup();
   vi.restoreAllMocks();
   setLanguage("en");
 });