Implement review remediation + PLG analytics SDK

- All 6 test architectures patched with Section 11 addendums
- P5 (cost) fully rewritten from 232 to ~600 lines
- PLG brainstorm + party mode advisory board results
- Analytics SDK v2 (PostHog Cloud, Zod strict, Lambda-safe)
- Analytics tests v2 (safeParse, no , no timestamp, no PII)
- Addresses all Gemini review findings across P1-P6

products/01-llm-cost-router/tests/analytics/analytics.spec.ts

@@ -0,0 +1,204 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { Analytics, EventSchema, EventName } from '../../src/analytics';
+import { PostHog } from 'posthog-node';
+
+vi.mock('posthog-node');
+
+describe('Analytics SDK (PostHog Cloud — v2 Post-Review)', () => {
+  let analytics: Analytics;
+  let mockPostHog: vi.Mocked<PostHog>;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockPostHog = new PostHog('phc_test_key', { host: 'https://us.i.posthog.com' }) as any;
+    analytics = new Analytics(mockPostHog);
+  });
+
+  // ── Schema Validation (Zod) ──────────────────────────────
+
+  describe('Event Taxonomy Validation', () => {
+    it('accepts valid account.signup.completed event', () => {
+      const event = {
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route' as const,
+        properties: { method: 'github_sso' },
+      };
+      expect(() => EventSchema.parse(event)).not.toThrow();
+    });
+
+    it('rejects events missing tenant_id', () => {
+      const event = {
+        name: EventName.SignupCompleted,
+        product: 'route',
+        properties: { method: 'email' },
+      };
+      expect(() => EventSchema.parse(event as any)).toThrow(/tenant_id/);
+    });
+
+    it('accepts valid activation event', () => {
+      const event = {
+        name: EventName.FirstDollarSaved,
+        tenant_id: 'tenant-123',
+        product: 'route' as const,
+        properties: { savings_amount: 1.50 },
+      };
+      expect(() => EventSchema.parse(event)).not.toThrow();
+    });
+
+    it('accepts valid upgrade event', () => {
+      const event = {
+        name: EventName.UpgradeCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route' as const,
+        properties: { plan: 'pro', mrr_increase: 49 },
+      };
+      expect(() => EventSchema.parse(event)).not.toThrow();
+    });
+  });
+
+  // ── track() Behavior ─────────────────────────────────────
+
+  describe('track()', () => {
+    it('captures valid events via PostHog client', () => {
+      const result = analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'email' },
+      });
+
+      expect(result).toBe(true);
+      expect(mockPostHog.capture).toHaveBeenCalledWith(
+        expect.objectContaining({
+          distinctId: 'tenant-123',
+          event: 'account.signup.completed',
+          properties: expect.objectContaining({
+            product: 'route',
+            method: 'email',
+          }),
+        })
+      );
+    });
+
+    it('does NOT include $set in track calls (use identify instead)', () => {
+      analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'github_sso' },
+      });
+
+      const captureCall = mockPostHog.capture.mock.calls[0][0];
+      expect(captureCall.properties).not.toHaveProperty('$set');
+    });
+
+    it('does NOT pass timestamp (let PostHog handle it to avoid clock skew)', () => {
+      analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'email' },
+      });
+
+      const captureCall = mockPostHog.capture.mock.calls[0][0];
+      expect(captureCall).not.toHaveProperty('timestamp');
+    });
+
+    it('returns false and does NOT call PostHog if base validation fails', () => {
+      const result = analytics.track({
+        name: 'invalid.event' as any,
+        tenant_id: 'tenant-123',
+        product: 'route',
+      });
+
+      expect(result).toBe(false);
+      expect(mockPostHog.capture).not.toHaveBeenCalled();
+    });
+
+    it('returns false if per-event property validation fails (strict schema)', () => {
+      const result = analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'invalid_method' }, // Not in enum
+      });
+
+      expect(result).toBe(false);
+      expect(mockPostHog.capture).not.toHaveBeenCalled();
+    });
+
+    it('rejects unknown properties (strict mode — no PII loophole)', () => {
+      const result = analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'email', email: 'user@example.com' }, // PII leak attempt
+      });
+
+      expect(result).toBe(false);
+      expect(mockPostHog.capture).not.toHaveBeenCalled();
+    });
+
+    it('does NOT flush after each track call (Lambda batching)', () => {
+      analytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'email' },
+      });
+
+      expect(mockPostHog.flushAsync).not.toHaveBeenCalled();
+    });
+  });
+
+  // ── identify() ───────────────────────────────────────────
+
+  describe('identify()', () => {
+    it('calls PostHog identify with tenant_id as distinctId', () => {
+      analytics.identify('tenant-123', { company: 'Acme' });
+
+      expect(mockPostHog.identify).toHaveBeenCalledWith(
+        expect.objectContaining({
+          distinctId: 'tenant-123',
+          properties: expect.objectContaining({
+            tenant_id: 'tenant-123',
+            company: 'Acme',
+          }),
+        })
+      );
+    });
+  });
+
+  // ── flush() ──────────────────────────────────────────────
+
+  describe('flush()', () => {
+    it('calls flushAsync on the PostHog client', async () => {
+      await analytics.flush();
+      expect(mockPostHog.flushAsync).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  // ── NoOp Client ──────────────────────────────────────────
+
+  describe('NoOp Client (missing API key)', () => {
+    it('does not throw when tracking without API key', () => {
+      const noopAnalytics = new Analytics(); // No client, no env var
+      const result = noopAnalytics.track({
+        name: EventName.SignupCompleted,
+        tenant_id: 'tenant-123',
+        product: 'route',
+        properties: { method: 'email' },
+      });
+      expect(result).toBe(true); // NoOp accepts everything silently
+    });
+  });
+
+  // ── Session Replay ───────────────────────────────────────
+
+  describe('Security', () => {
+    it('session replay is disabled', () => {
+      expect(analytics.isSessionReplayEnabled).toBe(false);
+    });
+  });
+});