test(preferences): add unit tests for PreferencesForm component

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

tests/int/preferences-form.int.spec.ts

@@ -0,0 +1,70 @@
+import { createElement } from "react";
+import { fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { PreferencesForm } from "@/components/frontend/account/PreferencesForm";
+import { updatePreferences } from "@/app/(frontend)/account/actions";
+
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({ refresh: vi.fn() }),
+}));
+
+vi.mock("@/app/(frontend)/account/actions", () => ({
+  updatePreferences: vi.fn(),
+}));
+
+class ResizeObserverMock implements ResizeObserver {
+  observe(_target: Element, _options?: ResizeObserverOptions): void {}
+
+  unobserve(_target: Element): void {}
+
+  disconnect(): void {}
+}
+
+globalThis.ResizeObserver = ResizeObserverMock;
+
+const mockedUpdatePreferences = vi.mocked(updatePreferences);
+
+describe("PreferencesForm", () => {
+  beforeEach(() => {
+    mockedUpdatePreferences.mockReset();
+    mockedUpdatePreferences.mockResolvedValue({ success: true });
+  });
+
+  it("submits all display, in-app, and Discord preferences", async () => {
+    render(
+      createElement(PreferencesForm, {
+        mutedAll: false,
+        mutedTypes: ["market:offer"],
+        showCallsign: false,
+        showVersionOverlay: true,
+        leadOrActual: "lead",
+        discordEnabled: false,
+        discordMutedTypes: [],
+      }),
+    );
+
+    fireEvent.click(screen.getByRole("switch", { name: "Show version overlay" }));
+    fireEvent.click(screen.getByRole("switch", { name: "Show callsign instead of display name" }));
+    fireEvent.click(screen.getByRole("switch", { name: "Mute all in-app notifications" }));
+    fireEvent.click(screen.getByRole("radio", { name: "Actual" }));
+    fireEvent.click(screen.getByRole("switch", { name: "Enable Discord notifications" }));
+    const discordMarketOffer = document.getElementById("discord-market-offer");
+    if (!(discordMarketOffer instanceof HTMLElement)) {
+      throw new Error("Discord market-offer switch was not rendered.");
+    }
+    fireEvent.click(discordMarketOffer);
+    fireEvent.click(screen.getByRole("button", { name: "Save preferences" }));
+
+    await waitFor(() => {
+      expect(mockedUpdatePreferences).toHaveBeenCalledWith({
+        mutedAll: true,
+        mutedTypes: ["market:offer"],
+        showCallsign: true,
+        showVersionOverlay: false,
+        leadOrActual: "actual",
+        discordEnabled: true,
+        discordMutedTypes: ["market:offer"],
+      });
+    });
+  });
+});