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");
 });

frontend/src/lib/useTags.dom.test.tsx

@@ -3,14 +3,21 @@
 // E30 (D1 A): the tag catalog as every reader sees it. A system (auto) tag is stored in English and
 // named in the reader's language; a user's own tag stays as they typed it, even when it happens to be
 // a vocabulary word.
-import { describe, expect, it, vi } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 import type { ReactNode } from "react";
-import { renderHook, waitFor } from "@testing-library/react";
+import { cleanup, renderHook, waitFor } from "@testing-library/react";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { setLanguage } from "../i18n";
 import { api, type Tag } from "./api";
 import { useTags } from "./useTags";
 
+// 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 tag = (id: number, name: string, system: boolean): Tag => ({
   id,
   name,
@@ -36,19 +43,15 @@ describe("the tag catalog", () => {
       { ...tag(5, "Hungarian", true), category: "language" },
     ]);
     setLanguage("hu");
-    try {
-      const { result } = renderHook(() => useTags(), { wrapper });
-      await waitFor(() => expect(result.current.data).toBeDefined());
-      expect(result.current.data!.map((tg) => tg.name)).toEqual([
-        "Oktatás",
-        "Utazás",
-        "Zene",
-        "Angol",
-        "Magyar",
-      ]);
-    } finally {
-      setLanguage("en");
-    }
+    const { result } = renderHook(() => useTags(), { wrapper });
+    await waitFor(() => expect(result.current.data).toBeDefined());
+    expect(result.current.data!.map((tg) => tg.name)).toEqual([
+      "Oktatás",
+      "Utazás",
+      "Zene",
+      "Angol",
+      "Magyar",
+    ]);
   });
 
   it("names an auto-tag in the reader's language, a user's tag as typed", async () => {
@@ -59,17 +62,13 @@ describe("the tag catalog", () => {
       tag(4, "Somethingnew", true), // an auto-tag the catalog does not name yet
     ]);
     setLanguage("hu");
-    try {
-      const { result } = renderHook(() => useTags(), { wrapper });
-      await waitFor(() => expect(result.current.data).toBeDefined());
-      expect(result.current.data!.map((tg) => tg.name)).toEqual([
-        "Egészség és fitnesz",
-        "Gaming",
-        "Magyar",
-        "Somethingnew",
-      ]);
-    } finally {
-      setLanguage("en");
-    }
+    const { result } = renderHook(() => useTags(), { wrapper });
+    await waitFor(() => expect(result.current.data).toBeDefined());
+    expect(result.current.data!.map((tg) => tg.name)).toEqual([
+      "Egészség és fitnesz",
+      "Gaming",
+      "Magyar",
+      "Somethingnew",
+    ]);
   });
 });