fix(audience-sdk-sample-app): adapt to flattened CDN global surface

The sample app and both READMEs were written against the nested
ImmutableAudience.Audience.init(...) shape that the CDN bundle
originally exposed. #2853 has since flattened the global to
ImmutableAudience.init(...) and removed the Audience class from
the CDN surface entirely — so the sample app's destructure
(\`var Audience = window.ImmutableAudience.Audience\`) now resolves
to undefined and every init call throws.

- sample-app.js: destructure \`init\` directly into a local
  \`audienceInit\` var and update all six call sites.
- sdk-sample-app/README.md: update the one remaining code snippet
  that showed Audience.init(...).
- sdk/README.md: update the tagline, rewrite the CDN quickstart to
  destructure \`init\` instead of \`Audience\`, and rephrase the
  "symbols attached to the global" paragraph to match the new
  surface (the CDN no longer exposes the Audience class itself).

Author: ImmutableJeffrey

packages/audience/sdk-sample-app/README.md

@@ -141,8 +141,8 @@ avoids a misleading "ok" log entry for a call that did nothing.
 `'CONSENT_SYNC_FAILED'`, `'NETWORK_ERROR'`, `'VALIDATION_REJECTED'`.
 Handle them in an `onError` callback passed at init time:
 
-```ts
-audience = Audience.init({
+```js
+const audience = window.ImmutableAudience.init({
   publishableKey: 'pk_imapik-test-...',
   onError: (err) => {
     switch (err.code) {

packages/audience/sdk-sample-app/sample-app.js

@@ -12,7 +12,7 @@
     return;
   }
 
-  var Audience = window.ImmutableAudience.Audience;
+  var audienceInit = window.ImmutableAudience.init;
   var AudienceError = window.ImmutableAudience.AudienceError;
   var IdentityType = window.ImmutableAudience.IdentityType;
   var SdkAudienceEvents = window.ImmutableAudience.AudienceEvents;
@@ -335,7 +335,7 @@
       return;
     }
     try {
-      audience = Audience.init(config);
+      audience = audienceInit(config);
       setInitState(true);
       currentConsent = config.consent;
       log('INIT', {
@@ -742,7 +742,7 @@
 
   function onInitEmptyKey() {
     try {
-      Audience.init({ publishableKey: '' });
+      audienceInit({ publishableKey: '' });
       log('Init with empty key', 'unexpected: init did not throw', 'err');
     } catch (err) {
       log('Init with empty key', {
@@ -768,7 +768,7 @@
     currentUserId = null;
     currentAnonId = null;
     try {
-      audience = Audience.init(readConfig());
+      audience = audienceInit(readConfig());
       currentConsent = $('initial-consent').value;
       setInitState(true);
       updateStatus();
@@ -790,7 +790,7 @@
     currentUserId = null;
     currentAnonId = null;
     try {
-      audience = Audience.init(withLiveConfig({
+      audience = audienceInit(withLiveConfig({
         baseUrl: DEAD_BASE_URL,
         consent: 'anonymous',
       }));
@@ -819,7 +819,7 @@
     currentUserId = null;
     currentAnonId = null;
     try {
-      audience = Audience.init(withLiveConfig({
+      audience = audienceInit(withLiveConfig({
         publishableKey: 'pk_imapik-test-revoked-0000000000000000',
         consent: 'anonymous',
       }));
@@ -848,7 +848,7 @@
     currentUserId = null;
     currentAnonId = null;
     try {
-      audience = Audience.init(withLiveConfig({
+      audience = audienceInit(withLiveConfig({
         baseUrl: DEAD_BASE_URL,
         consent: 'none',
       }));

packages/audience/sdk/README.md

@@ -40,7 +40,7 @@ yarn add @imtbl/audience
 ```
 
 For the CDN build, drop one `<script>` tag into your HTML and call
-`ImmutableAudience.Audience.init({...})` — no bundler, no `npm install`.
+`ImmutableAudience.init({...})` — no bundler, no `npm install`.
 Once `@imtbl/audience` is published, the bundle URL will be
 `https://cdn.jsdelivr.net/npm/@imtbl/audience@<version>/dist/cdn/imtbl-audience.global.js`
 (replace `<version>` with a specific release tag).
@@ -71,10 +71,10 @@ audience.shutdown();
 <script src="https://cdn.jsdelivr.net/npm/@imtbl/audience@<version>/dist/cdn/imtbl-audience.global.js"></script>
 <script>
   const {
-    Audience, AudienceError, AudienceEvents,
+    init, AudienceError, AudienceEvents,
     IdentityType, canTrack, canIdentify,
   } = window.ImmutableAudience;
-  const audience = Audience.init({
+  const audience = init({
     publishableKey: 'pk_imapik-test-...',
     consent: 'anonymous',
     onError: (err) => console.error(err.code, err.message),
@@ -84,10 +84,11 @@ audience.shutdown();
 </script>
 ```
 
-The CDN bundle attaches the same runtime symbols that ESM consumers
-import — `Audience`, `AudienceError`, `AudienceEvents`, `IdentityType`,
-`canTrack`, `canIdentify`, and `version` — so no snippet is reachable
-on one path but not the other.
+The CDN bundle attaches `init` (the same static factory ESM consumers
+call as `Audience.init({...})`) alongside `AudienceError`,
+`AudienceEvents`, `IdentityType`, `canTrack`, `canIdentify`, and
+`version`, so every runtime helper an ESM consumer needs is reachable
+from the CDN global too.
 
 ## Error handling