test(frontend): cover NewSessionDialog model degradation + invalidate sessions on resume

- Add NewSessionDialog.test.tsx covering §9 graceful degradation:
  empty models -> free-text input; non-empty models -> dropdown; plus a
  createSession body-keys assertion
- Normalize model entries to {value,label} so object-shaped models
  ({provider,id}) render correctly in the dropdown (was assuming strings)
- NavSessions: invalidate the ["sessions"] query after a successful
  resumeSession so the list/status refreshes immediately

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/shell/NewSessionDialog.test.tsx

@@ -0,0 +1,82 @@
+// frontend/src/shell/NewSessionDialog.test.tsx
+import { render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { http, HttpResponse } from "msw";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { server } from "../test/msw";
+import { NewSessionDialog } from "./NewSessionDialog";
+
+function renderDialog() {
+  const onCreated = vi.fn();
+  const client = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  render(
+    <QueryClientProvider client={client}>
+      <NewSessionDialog onCreated={onCreated} />
+    </QueryClientProvider>,
+  );
+  return { onCreated };
+}
+
+beforeEach(() => {
+  server.use(
+    http.get("http://localhost:8787/workspaces", () =>
+      HttpResponse.json([{ name: "default", file: "default.db" }]),
+    ),
+    http.post("http://localhost:8787/sessions", () =>
+      HttpResponse.json({ id: "s1" }),
+    ),
+  );
+});
+
+test("§9 degradation: empty models -> model field is a FREE-TEXT input, not a select", async () => {
+  server.use(
+    http.get("http://localhost:8787/models", () => HttpResponse.json({ models: [] })),
+  );
+  renderDialog();
+  await userEvent.click(screen.getByRole("button", { name: /nuova/i }));
+
+  // Free-text model input present; no model dropdown.
+  const freetext = await screen.findByTestId("model-freetext");
+  expect(freetext.tagName).toBe("INPUT");
+  // The only <select> in the dialog is the workspace one (id nsd-workspace).
+  expect(screen.queryByRole("combobox", { name: /modello/i })).not.toBeInTheDocument();
+});
+
+test("§9: non-empty models -> model field is a dropdown (select), not free text", async () => {
+  server.use(
+    http.get("http://localhost:8787/models", () =>
+      HttpResponse.json({ models: [{ provider: "zai", id: "glm-5.2" }] }),
+    ),
+  );
+  renderDialog();
+  await userEvent.click(screen.getByRole("button", { name: /nuova/i }));
+
+  // Model dropdown present; no free-text input.
+  const modelSelect = await screen.findByRole("combobox", { name: /modello/i });
+  expect(modelSelect.tagName).toBe("SELECT");
+  expect(screen.queryByTestId("model-freetext")).not.toBeInTheDocument();
+  // Option label combines provider/id.
+  expect(screen.getByRole("option", { name: "zai/glm-5.2" })).toBeInTheDocument();
+});
+
+test("submitting calls createSession with the expected body keys", async () => {
+  let body: unknown = null;
+  server.use(
+    http.get("http://localhost:8787/models", () => HttpResponse.json({ models: [] })),
+    http.post("http://localhost:8787/sessions", async ({ request }) => {
+      body = await request.json();
+      return HttpResponse.json({ id: "s1" });
+    }),
+  );
+  const { onCreated } = renderDialog();
+  await userEvent.click(screen.getByRole("button", { name: /nuova/i }));
+
+  const textarea = await screen.findByLabelText(/domanda/i);
+  await userEvent.type(textarea, "Quante vendite nel 2025?");
+  await userEvent.click(screen.getByRole("button", { name: /^crea$/i }));
+
+  await waitFor(() => {
+    expect(body).toEqual({ workspace: "default", question: "Quante vendite nel 2025?" });
+  });
+  await waitFor(() => expect(onCreated).toHaveBeenCalledWith("s1"));
+});