fix(api): a write that hit a connection failure is still reported, and every failure is reported once

Deep-review round 4, the "one report per failure" contract round 3 introduced.

- `req` marked gateway (502/503/504) and network failures "already reported" because they raise
  the connection notice. But that notice is about connectivity and removes itself on the very next
  answer — which every caller's own resync refetch fetches at once — so a delete that hit a
  keepalive reset flashed the notice and was then reported nowhere, the list still there. Only the
  durable reports (the error dialog, the 401 sign-out) count now; the caller says the action failed.
- A connection notice the user closed swallowed every later one for the rest of the visit; it is
  raised again.
- `req` and `uploadReq` share one failure policy (`reportFailure`). The upload copy had drifted: a
  502 opened the blocking "Server error (502)" dialog and cleared a notice that was still true.
- A taken Plex collection name is a structured 409, localized, and the create/rename calls are
  quiet: it was an English dialog plus a Hungarian toast. `notifyCollectionEditError` is gone.
- The mutation onErrors that toasted unconditionally after a non-quiet request (invite approve /
  deny / add, demo whitelist, audit clear, scheduler, share, full history, edit, config tests, tag
  attach) go through `notifyActionError`; the playlist delete's hand-rolled copy of it too (it takes
  a level now). The user role / suspend / delete actions had no onError at all: a user deleted in
  another tab failed silently and stayed listed — now said, and the list refetched.

frontend/src/lib/actionErrors.test.ts

@@ -5,28 +5,37 @@ import { describe, it, expect, vi, beforeEach } from "vitest";
 
 // Spy on the toast sink so we can assert exactly what each error maps to.
 vi.mock("./notifications", () => ({ notify: vi.fn(() => 0) }));
+vi.mock("./errorDialog", () => ({ reportError: vi.fn() }));
 
 import { HttpError, api } from "./api";
 import { notify } from "./notifications";
-import { notifyActionError, notifyCollectionEditError } from "./actionErrors";
+import { reportError } from "./errorDialog";
+import { notifyActionError } from "./actionErrors";
+import i18n from "../i18n";
 
 const notifyMock = vi.mocked(notify);
-beforeEach(() => notifyMock.mockClear());
+beforeEach(() => {
+  notifyMock.mockClear();
+  vi.mocked(reportError).mockClear();
+});
 
-describe("notifyCollectionEditError", () => {
-  it("maps a backend 409 to the friendly nameTaken message (not the raw server detail)", () => {
-    notifyCollectionEditError(new HttpError(409, "already exists"), "EDIT_FAILED", "NAME_TAKEN");
-    expect(notifyMock).toHaveBeenCalledWith({ level: "error", message: "NAME_TAKEN" });
-  });
-
-  it("falls back to the server detail for a non-409 HttpError", () => {
-    notifyCollectionEditError(new HttpError(500, "server boom"), "EDIT_FAILED", "NAME_TAKEN");
-    expect(notifyMock).toHaveBeenCalledWith({ level: "error", message: "server boom" });
-  });
-
-  it("falls back to the generic edit-failed message for a non-HttpError", () => {
-    notifyCollectionEditError(new Error("network"), "EDIT_FAILED", "NAME_TAKEN");
-    expect(notifyMock).toHaveBeenCalledWith({ level: "error", message: "EDIT_FAILED" });
+describe("a Plex collection name that is already taken", () => {
+  it("is reported once, in the reader's language", async () => {
+    // The 409 was a bare English string: the global error dialog showed it in English, and the
+    // editor's own toast said the same thing again, translated (deep-review round 4).
+    vi.spyOn(globalThis, "fetch").mockResolvedValue(
+      new Response(JSON.stringify({ detail: { code: "collection", reason: "name_taken" } }), {
+        status: 409,
+        headers: { "content-type": "application/json" },
+      }),
+    );
+    const err = await api.plexCreateCollection("1", "Marvel", "m1").catch((e: unknown) => e);
+    notifyMock.mockClear();
+    notifyActionError(err, "EDIT_FAILED");
+    expect(notifyMock.mock.calls).toEqual([
+      [{ level: "error", message: i18n.t("plex.collection.nameTaken") }],
+    ]);
+    expect(reportError).not.toHaveBeenCalled();
   });
 });