fix(ui): the export dialog reports a failure only once the job has settled

frontend/ui-core/src/screens/DatasetScreen.tsx

@@ -1001,7 +1001,9 @@ function ExportDialog({
   const lost = failure !== null && needsConsent ? lostClasses(failure.detail) : null;
   const running = exportRelease.isPending || (job.data !== undefined && !isSettled(job.data));
   const stopped =
-    job.data !== undefined && job.data.state !== "succeeded" ? job.data : null;
+    job.data !== undefined && isSettled(job.data) && job.data.state !== "succeeded"
+      ? job.data
+      : null;
 
   function run(allowLossy: boolean): void {
     setSaved(false);

frontend/ui-core/src/screens/dataset.test.tsx

@@ -10,7 +10,7 @@
  */
 
 import { QueryClient } from "@tanstack/react-query";
-import { render, screen, waitFor, within } from "@testing-library/react";
+import { cleanup, render, screen, waitFor, within } from "@testing-library/react";
 import { userEvent } from "@testing-library/user-event";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import type { JSX, ReactNode } from "react";
@@ -715,6 +715,16 @@ describe("export, and the third gate word", () => {
     expect(badge.className).toContain("text-primary");
   });
 
+  it("shows no failure while the export is still queued or running", async () => {
+    // A job that has not settled has nothing to explain yet; the failure
+    // sentence belongs to a job that stopped, never to one still working.
+    await exportWith("queued");
+    expect(screen.queryByTestId("export-job-error")).toBeNull();
+    cleanup();
+    await exportWith("running");
+    expect(screen.queryByTestId("export-job-error")).toBeNull();
+  });
+
   it("says a finished export is done, in the success token (#391)", async () => {
     const badge = await exportWith("succeeded");
     expect(badge.textContent).toContain("Done");