fix: surface reviewer response failures

frontend/src/shell/WidgetHost.response.test.tsx

@@ -0,0 +1,53 @@
+import { act, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { http, HttpResponse } from "msw";
+import { server } from "../test/msw";
+import { useSessionStore } from "../store/sessionStore";
+import { WidgetHost } from "./WidgetHost";
+
+beforeEach(() => useSessionStore.getState().resetSession());
+
+test("a gate choice shows progress, prevents duplicate clicks, and confirms delivery", async () => {
+  let release!: () => void;
+  const held = new Promise<void>((resolve) => { release = resolve; });
+  let requests = 0;
+  server.use(http.post("/api/sessions/s1/response", async () => {
+    requests += 1;
+    await held;
+    return new HttpResponse(null, { status: 204 });
+  }));
+  useSessionStore.setState({
+    pendingWidget: {
+      id: "gate-1",
+      widget: "select",
+      options: [{ id: "recommended", label: "Recommended answer" }],
+    },
+  });
+
+  const user = userEvent.setup();
+  render(<WidgetHost sessionId="s1" />);
+  const choice = screen.getByRole("button", { name: "Recommended answer" });
+  await user.click(choice);
+
+  expect(screen.getByRole("status")).toHaveTextContent("Sending response");
+  expect(choice).toBeDisabled();
+  await user.click(choice);
+  expect(requests).toBe(1);
+
+  act(() => release());
+  await waitFor(() => expect(useSessionStore.getState().pendingWidget).toBeNull());
+  expect(useSessionStore.getState().toasts.at(-1)).toEqual({
+    level: "success",
+    text: "Response sent. The model is continuing.",
+  });
+
+  act(() => useSessionStore.setState({
+    pendingWidget: {
+      id: "gate-2",
+      widget: "select",
+      options: [{ id: "next", label: "Next answer" }],
+    },
+  }));
+  expect(screen.getByRole("button", { name: "Next answer" })).toBeEnabled();
+  expect(screen.queryByRole("status")).not.toBeInTheDocument();
+});