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/SettingsPanel.tsx

@@ -6,6 +6,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { Bell, Check, Loader2, Monitor, RefreshCw, Trash2, User } from "lucide-react";
 import { SCHEMES, type Scheme, type ThemePrefs } from "../lib/theme";
 import { api, HttpError, type Me } from "../lib/api";
+import { notifyActionError } from "../lib/actionErrors";
 import { LS, useAccountPersistedState } from "../lib/storage";
 import Avatar from "./ui/Avatar";
 import { notify, type NotifSettings } from "../lib/notifications";
@@ -553,10 +554,11 @@ function PlexWatchSync() {
   };
 
   // No onError on these: they're Plex, not YouTube (notifyYouTubeActionError would wrongly say
-  // "connect YouTube"), and their 409/500 are already surfaced by the global error modal — a caller
-  // toast would double it. Actual import failures come back as 200 {error}, handled by announce.
+  // "connect YouTube"). Their 409/500 open the global error dialog and the rest go to the app-wide
+  // reporter (lib/queryClient). Actual import failures come back as 200 {error}, handled by announce.
   const toggle = useMutation({
     mutationFn: (next: boolean) => api.plexWatchSetLink(next),
+    meta: { failTitle: "errors.writeFailed.plexWatchLink" },
     onSuccess: (res) => {
       qc.setQueryData(qk.plexWatchLink(), res);
       announce(res.import);
@@ -564,6 +566,7 @@ function PlexWatchSync() {
   });
   const reimport = useMutation({
     mutationFn: () => api.plexWatchImport(),
+    meta: { failTitle: "errors.writeFailed.plexWatchImport" },
     onSuccess: (res) => {
       qc.setQueryData(qk.plexWatchLink(), res);
       announce(res.import);
@@ -637,10 +640,13 @@ export function DownloadAuth() {
       notify({ level: "success", message: t("settings.downloadAuth.saved") });
     },
     // Validation errors (empty / not-a-cookies.txt) surface via the global error modal, which
-    // localizes the structured { code: "cookies" } detail (see lib/api core localizeDetail).
+    // localizes the structured { code: "cookies" } detail (see lib/api core localizeDetail); the
+    // statuses it does not cover go to the app-wide reporter.
+    meta: { failTitle: "settings.downloadAuth.failed" },
   });
   const remove = useMutation({
     mutationFn: (host: string) => api.deleteDownloadCredential(host),
+    meta: { failTitle: "errors.writeFailed.downloadCookiesRemove" },
     onSuccess: (res) => {
       qc.setQueryData(qk.downloadCredentials(), res);
       notify({ level: "success", message: t("settings.downloadAuth.removed") });
@@ -781,8 +787,10 @@ function Account({ me, onOpenWizard }: { me: Me; onOpenWizard: () => void }) {
       await api.deleteAccount();
       // Session cleared server-side → /api/me 401s → Welcome. The flag shows the confirmation banner.
       window.location.href = "/?deleted=1";
-    } catch {
-      /* the global error dialog surfaces the reason (e.g. last admin) */
+    } catch (e) {
+      // A refusal with a reason (the last admin, a 409) is already in the global error dialog, which
+      // the reporter skips; anything else used to end the confirmed delete with nothing said.
+      notifyActionError(e, t("errors.writeFailed.deleteAccount"));
     }
   };
   return (