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/lib/api/core.ts

@@ -23,10 +23,18 @@ export const uiLang = (): string => i18n.language.split("-")[0] || "en";
 // removes itself on the next answer — which every caller's own resync refetch fetches at once. Marked
 // as reported, a delete that hit a keepalive reset (a 502) flashed the notice for a moment and was
 // then reported nowhere at all, the list still there (deep-review round 4).
+//
+// A caller that reports a failure itself marks it too (`notifyActionError` does), which is what lets
+// the ONE app-wide mutation reporter (lib/queryClient) stay quiet for a mutation whose own `onError`
+// already said something, and speak for every one that did not.
 const reported = new WeakSet<object>();
 export function alreadyReported(err: unknown): boolean {
   return typeof err === "object" && err !== null && reported.has(err);
 }
+/** Record that this failure is on screen now, so nothing reports it a second time. */
+export function markReported(err: unknown): void {
+  if (typeof err === "object" && err !== null) reported.add(err);
+}
 
 /** What an upload the USER cancelled rejects with. A cancel is not a failure to report, and the
  *  only other rejection carrying status 0 is a genuine network drop, which IS worth reporting — so