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.ts

@@ -0,0 +1,23 @@
+import type {
+  AnalyticsAttributeValue,
+  AnalyticsUser,
+  IAnalytics,
+} from "./analytics.interface";
+
+export class NoopAnalytics implements IAnalytics {
+  track(
+    _event: string,
+    _attributes?: Record<string, AnalyticsAttributeValue>,
+  ): void {}
+  identify(
+    _user: AnalyticsUser,
+    _attributes?: Record<string, AnalyticsAttributeValue>,
+  ): void {}
+  pageView(
+    _path: string,
+    _attributes?: Record<string, AnalyticsAttributeValue>,
+  ): void {}
+  flush(): Promise<void> {
+    return Promise.resolve();
+  }
+}