feat(ai-character): Mock Preview 모드 구현

tests/e2e/mock-mode-boundary.spec.ts

@@ -0,0 +1,20 @@
+import { expect, test } from "@playwright/test";
+
+test("registers a browser MSW worker in explicit mock mode", async ({ page }) => {
+  // Given
+  const expectedWorkerRegistration = true;
+
+  // When
+  await page.goto("/");
+
+  // Then
+  await expect
+    .poll(() =>
+      page.evaluate(async () => {
+        const registration = await navigator.serviceWorker.ready;
+
+        return registration.active?.scriptURL.endsWith("/mockServiceWorker.js") ?? false;
+      }),
+    )
+    .toBe(expectedWorkerRegistration);
+});