feat(pixel): add identityType parameter to identify()

Add required identityType parameter (second arg) to Pixel.identify() so
the backend can distinguish which identity system a user ID belongs to
(passport, steam, epic, etc.). Uses the shared IdentityType union from
@imtbl/audience-core for parity with the web SDK.

Closes SDK-77

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

Author: bkbooth

packages/audience/pixel/src/pixel.test.ts

@@ -219,20 +219,21 @@ describe('Pixel', () => {
   });
 
   describe('identify', () => {
-    it('enqueues identify message at full consent', () => {
+    it('enqueues identify message with identityType at full consent', () => {
       mockGetOrCreateSession.mockReturnValue({ sessionId: 'session-abc', isNew: false });
 
       const pixel = new Pixel();
       activePixel = pixel;
       pixel.init({ key: 'pk_test', environment: 'dev', consent: 'full' });
       mockEnqueue.mockClear();
 
-      pixel.identify('user-1', { email: 'test@example.com' });
+      pixel.identify('user-1', 'passport', { email: 'test@example.com' });
 
       expect(mockEnqueue).toHaveBeenCalledWith(
         expect.objectContaining({
           type: 'identify',
           userId: 'user-1',
+          identityType: 'passport',
           surface: 'pixel',
           traits: expect.objectContaining({
             email: 'test@example.com',
@@ -242,12 +243,31 @@ describe('Pixel', () => {
       );
     });
 
+    it('enqueues identify message without traits', () => {
+      mockGetOrCreateSession.mockReturnValue({ sessionId: 'session-abc', isNew: false });
+
+      const pixel = new Pixel();
+      activePixel = pixel;
+      pixel.init({ key: 'pk_test', environment: 'dev', consent: 'full' });
+      mockEnqueue.mockClear();
+
+      pixel.identify('steam-id-123', 'steam');
+
+      expect(mockEnqueue).toHaveBeenCalledWith(
+        expect.objectContaining({
+          type: 'identify',
+          userId: 'steam-id-123',
+          identityType: 'steam',
+        }),
+      );
+    });
+
     it('does not enqueue identify at anonymous consent', () => {
       const pixel = new Pixel();
       activePixel = pixel;
       pixel.init({ key: 'pk_test', environment: 'dev', consent: 'anonymous' });
 
-      pixel.identify('user-1');
+      pixel.identify('user-1', 'passport');
       // Only the auto page view + session_start, no identify
       const calls = mockEnqueue.mock.calls.map((c: unknown[]) => (c[0] as Record<string, unknown>));
       expect(calls.find((c) => c.type === 'identify')).toBeUndefined();

packages/audience/pixel/src/pixel.ts

@@ -6,6 +6,7 @@ import type {
   IdentifyMessage,
   UserTraits,
   ConsentManager,
+  IdentityType,
 } from '@imtbl/audience-core';
 import {
   MessageQueue,
@@ -147,7 +148,7 @@ export class Pixel {
     this.queue!.enqueue(message);
   }
 
-  identify(userId: string, traits?: UserTraits): void {
+  identify(userId: string, identityType: IdentityType, traits?: UserTraits): void {
     if (!this.isReady() || this.consent!.level !== 'full') return;
 
     this.userId = userId;
@@ -158,6 +159,7 @@ export class Pixel {
       ...this.buildBase(),
       type: 'identify',
       userId,
+      identityType,
       traits: {
         ...traits,
         sessionId,