feat(core-analytics): add IAnalytics interface, types, and NoopAnalytics

Replaces generator placeholder with IAnalytics interface (track, identify,
pageView, flush), AnalyticsAttributeValue + AnalyticsUser types, and
NoopAnalytics implementation. Adds sibling tests covering all four methods
with 100% coverage. All conformance + coverage gates pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-analytics/src/noop-analytics.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, it } from "vitest";
+import { NoopAnalytics } from "@/noop-analytics";
+
+describe("NoopAnalytics", () => {
+  it("track() does not throw with event name only", () => {
+    const analytics = new NoopAnalytics();
+    expect(() => analytics.track("page_viewed")).not.toThrow();
+  });
+
+  it("track() does not throw with event name and attributes", () => {
+    const analytics = new NoopAnalytics();
+    expect(() =>
+      analytics.track("button_clicked", {
+        label: "signup",
+        count: 1,
+        active: true,
+      }),
+    ).not.toThrow();
+  });
+
+  it("identify() does not throw with user only", () => {
+    const analytics = new NoopAnalytics();
+    expect(() => analytics.identify({ id: "user-123" })).not.toThrow();
+  });
+
+  it("identify() does not throw with user and attributes", () => {
+    const analytics = new NoopAnalytics();
+    expect(() =>
+      analytics.identify({ id: "user-123" }, { plan: "pro", trial: false }),
+    ).not.toThrow();
+  });
+
+  it("pageView() does not throw with path only", () => {
+    const analytics = new NoopAnalytics();
+    expect(() => analytics.pageView("/dashboard")).not.toThrow();
+  });
+
+  it("pageView() does not throw with path and attributes", () => {
+    const analytics = new NoopAnalytics();
+    expect(() =>
+      analytics.pageView("/dashboard", { referrer: "/home", duration: 120 }),
+    ).not.toThrow();
+  });
+
+  it("flush() resolves without throwing", async () => {
+    const analytics = new NoopAnalytics();
+    await expect(analytics.flush()).resolves.toBeUndefined();
+  });
+
+  it("flush() returns a Promise", () => {
+    const analytics = new NoopAnalytics();
+    expect(analytics.flush()).toBeInstanceOf(Promise);
+  });
+});