feat(audience): add CDN bundle, demo page, and README

- CDN IIFE entry point (window.ImmutableWebSDK), self-contained bundle
- Interactive demo page for end-to-end testing
- README with install, API reference, consent, cookies, CDN usage

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ImmutableJeffrey

packages/audience/web/README.md

@@ -0,0 +1,154 @@
+# @imtbl/audience-web-sdk
+
+Consent-aware event tracking and identity management for web surfaces. Part of the Immutable Audience platform.
+
+## Install
+
+```bash
+npm install @imtbl/audience-web-sdk
+```
+
+## Quick Start
+
+```typescript
+import { ImmutableWebSDK } from '@imtbl/audience-web-sdk';
+
+const sdk = ImmutableWebSDK.init({
+  publishableKey: 'pk_imtbl_...',
+  environment: 'production',
+  consent: 'anonymous',
+});
+
+sdk.track('purchase', { currency: 'USD', value: 9.99, itemId: 'sword_01' });
+sdk.page();
+```
+
+## Initialisation
+
+```typescript
+const sdk = ImmutableWebSDK.init({
+  publishableKey: 'pk_imtbl_...',   // Required — from Immutable Hub
+  environment: 'production',         // 'dev' | 'sandbox' | 'production'
+  consent: 'none',                   // 'none' | 'anonymous' | 'full' (default: 'none')
+  consentSource: 'CookieBannerV2',   // Identifies the consent source (default: 'WebSDK')
+  debug: false,                      // Log all events to console (default: false)
+  cookieDomain: '.studio.com',       // Cross-subdomain cookie sharing (optional)
+  flushInterval: 5000,               // Queue flush interval in ms (default: 5000)
+  flushSize: 20,                     // Queue flush size threshold (default: 20)
+});
+```
+
+## Consent
+
+The SDK defaults to `none` — no events are collected until consent is explicitly set.
+
+```typescript
+sdk.setConsent('anonymous');  // Anonymous tracking (no PII)
+sdk.setConsent('full');       // Full tracking (PII via identify)
+sdk.setConsent('none');       // Stop tracking, purge queue, clear cookies
+```
+
+Consent is:
+- **Persisted locally** via `_imtbl_consent` cookie (shared with the pixel)
+- **Synced server-side** via `PUT /v1/audience/tracking-consent`
+
+| Level | Behaviour |
+|-------|-----------|
+| `none` | SDK is inert. No events collected. Queue purged on downgrade. |
+| `anonymous` | Events collected with anonymous ID only. `identify()` calls are discarded. |
+| `full` | Full collection. `identify()` sends. `userId` included on events. |
+
+**On downgrade to `none`:** queue purged, `imtbl_anon_id` and `_imtbl_sid` cookies cleared.
+**On downgrade from `full` to `anonymous`:** identify messages purged, `userId` stripped from queued events.
+
+## Auto-Tracked Events
+
+The SDK automatically fires these events. Studios do not call them.
+
+| Event | When | Properties |
+|-------|------|------------|
+| `session_start` | SDK init with no active session cookie | `sessionId` |
+| `session_end` | `shutdown()` called | `sessionId`, `duration` (seconds) |
+
+## Event Tracking
+
+```typescript
+sdk.track('sign_up', { method: 'google' });
+sdk.track('purchase', { currency: 'USD', value: 9.99 });
+sdk.track('wishlist_add', { gameId: 'game_123', source: 'landing_page' });
+sdk.track('beta_key_redeemed', { source: 'influencer' });
+```
+
+## Page Tracking
+
+Call `sdk.page()` on route changes. Attribution context (UTMs, click IDs, referrer, landing page) is automatically attached to the first page view.
+
+```typescript
+sdk.page();
+sdk.page({ section: 'shop', category: 'weapons' });
+```
+
+## Identity
+
+```typescript
+// Identify a known user (requires full consent)
+sdk.identify('user@example.com', 'email');
+sdk.identify('76561198012345', 'steam');
+sdk.identify('passport_sub_abc', 'passport', {
+  email: 'user@example.com',
+  name: 'Player One',
+});
+
+// Identify with traits only (anonymous, no userId)
+sdk.identify({ source: 'steam', steamId: '76561198012345' });
+
+// Link two identities (same player, different providers)
+sdk.alias(
+  { uid: '76561198012345', provider: 'steam' },
+  { uid: 'user@example.com', provider: 'email' },
+);
+
+// Reset on logout (new anonymous ID, clears userId)
+sdk.reset();
+```
+
+## Queue & Lifecycle
+
+```typescript
+await sdk.flush();     // Force flush all queued events
+sdk.shutdown();        // Flush remaining events, stop the SDK
+```
+
+Events are batched and flushed every 5 seconds or when 20 messages accumulate. On page unload (`visibilitychange` / `pagehide`), remaining events are flushed via `fetch` with `keepalive: true`.
+
+## CDN Usage
+
+For sites without a bundler:
+
+```html
+<script src="https://cdn.immutable.com/web-sdk/v1/imtbl-web.js"></script>
+<script>
+  var sdk = window.ImmutableWebSDK.init({
+    publishableKey: 'pk_imtbl_...',
+    environment: 'production',
+    consent: 'anonymous',
+  });
+
+  sdk.track('signup_started');
+  sdk.identify('user@example.com', 'email');
+</script>
+```
+
+## Cookies
+
+All cookies are first-party, `SameSite=Lax`, `Secure` on HTTPS, and shared with the pixel:
+
+| Cookie | Lifetime | Purpose |
+|--------|----------|---------|
+| `imtbl_anon_id` | 2 years | Anonymous device ID |
+| `_imtbl_sid` | 30 min (rolling) | Session continuity |
+| `_imtbl_consent` | 1 year | Consent state |
+
+## Wire Format
+
+Events are sent to `POST /v1/audience/messages` with the `x-immutable-publishable-key` header. All messages include `surface: 'web'` and follow the backend OpenAPI spec.