fix(ui): a write that fails says what failed and why, wherever it fails

`req` opens its blocking dialog for 400/409/422/5xx only. A 403/404/429 was left to the caller and a
502-504 or lost connection got just the self-clearing connection notice, so 34 mutations without a
reporting onError and 15 direct api writes with a bare or missing catch failed in silence: a hidden
channel that snapped back, a share link that never revoked, a confirmed account delete that ended
with nothing said.

- lib/queryClient: one MutationCache reporter. react-query awaits it BEFORE the mutation's own
  onError, so it waits a task and skips a failure the site already reported; the toast title comes
  from `meta.failTitle`, `meta.errorShownInline` opts out.
- notifyActionError: title names WHAT failed, the line under it says WHY (`failureReason`: a
  structured localized detail, else the status). It marks the error reported (`markReported`), so
  nothing reports one failure twice; `notifyKnownFailure` for a site's own specific sentence.
- Every silent site named (45 new HU/EN titles, 4 reasons). Stale "the global dialog shows it"
  comments corrected on the job actions, channel block, Plex sync, cookies, download enqueue,
  account delete and usePref.
- Channels passed the tag hook's channel id to the reporter as the error; the tag and priority hooks
  now report themselves, with the real error.
- A contract test keeps every useMutation naming its failure; CLAUDE.md gains the pattern row.
- history.dom.test: the "navigates only once the entries are back" assertion raced an async act's
  macrotask flush (1 in 5 runs); it now asserts from a later popstate listener.

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

@@ -19,7 +19,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 });
 vi.mock("./ConfirmProvider", () => ({ useConfirm: () => async () => true }));
 const { notify } = vi.hoisted(() => ({
-  notify: vi.fn((_n: { level: string; message: string }) => 0),
+  notify: vi.fn((_n: { level: string; title?: string; message: string }) => 0),
 }));
 vi.mock("../lib/notifications", async (importOriginal) => ({
   ...(await importOriginal<typeof import("../lib/notifications")>()),
@@ -28,6 +28,7 @@ vi.mock("../lib/notifications", async (importOriginal) => ({
 
 import PlexCollectionEditor from "./PlexCollectionEditor";
 import UploadDialog from "./UploadDialog";
+import DownloadDialog from "./DownloadDialog";
 import { api, HttpError } from "../lib/api";
 
 beforeAll(() => {
@@ -48,7 +49,9 @@ afterEach(() => {
   vi.restoreAllMocks();
 });
 
-const errors = () => notify.mock.calls.filter(([n]) => n.level === "error").map(([n]) => n.message);
+// What failed, as the toast names it: the title (E11 S2b — the title says WHAT, the line under it WHY).
+const errors = () =>
+  notify.mock.calls.filter(([n]) => n.level === "error").map(([n]) => n.title ?? n.message);
 const client = () => new QueryClient({ defaultOptions: { queries: { retry: false } } });
 
 describe("the Plex collection editor", () => {
@@ -144,3 +147,20 @@ describe("the upload dialog", () => {
     expect(errors()).toEqual([]);
   });
 });
+
+describe("the download dialog", () => {
+  it("names a queueing the server refused with no dialog of its own", async () => {
+    // Its catch said "the global error dialog already surfaced the reason" — true for a quota 422,
+    // not for a 403/404/429 or a lost connection, where the dialog just stayed open (E11 S2b).
+    vi.spyOn(api, "downloadProfiles").mockResolvedValue([{ id: 1, name: "Best" }] as never);
+    vi.spyOn(api, "enqueueDownload").mockRejectedValue(new HttpError(403, "nope"));
+    render(
+      <QueryClientProvider client={client()}>
+        <DownloadDialog source="https://example.com/v" onClose={() => {}} />
+      </QueryClientProvider>,
+    );
+    await screen.findByText("Best");
+    fireEvent.click(screen.getByText("downloads.dialog.submit"));
+    await waitFor(() => expect(errors()).toEqual(["errors.writeFailed.enqueueDownload"]));
+  });
+});