feat(audience): expose typed event surface and autocomplete (SDK-116)

- Widen track() generic constraint to `AudienceEventName | string & {}`.
  IntelliSense surfaces the 11 predefined event names at `sdk.track('|`.
- Export `AudienceEventName` and `PropsFor<E>` from the package root.
- Note predefined-event type enforcement in track()'s JSDoc.

Addresses PR #2850 review feedback.

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

Author: ImmutableJeffrey

packages/audience/sdk/src/events.ts

@@ -133,6 +133,8 @@ interface EventPropsMap {
   link_clicked: LinkClickedProperties;
 }
 
+export type AudienceEventName = keyof EventPropsMap;
+
 /**
  * Event name → property type. Falls back to `Record<string, unknown>` for
  * unknown names. Used by `sdk.track()` to type-check property shapes at the

packages/audience/sdk/src/index.ts

@@ -3,12 +3,14 @@ export { AudienceEvents } from './events';
 export { IdentityType } from '@imtbl/audience-core';
 export type { AudienceConfig } from './types';
 export type {
+  AudienceEventName,
   EmailAcquiredProperties,
   GameLaunchProperties,
   GamePageViewedProperties,
   LinkClickedProperties,
   ProgressionProperties,
   ProgressionStatus,
+  PropsFor,
   PurchaseProperties,
   ResourceFlow,
   ResourceProperties,

packages/audience/sdk/src/sdk.ts

@@ -31,7 +31,7 @@ import {
   SESSION_END,
 } from '@imtbl/audience-core';
 import { DebugLogger } from './debug';
-import type { PropsFor } from './events';
+import type { AudienceEventName, PropsFor } from './events';
 import type { AudienceConfig } from './types';
 import {
   LIBRARY_NAME, LIBRARY_VERSION, LOG_PREFIX, DEFAULT_CONSENT_SOURCE,
@@ -239,9 +239,11 @@ export class Audience {
   /**
    * Record a player action like a purchase, sign-up, or game launch.
    * Pass the event name and any properties you want to analyse later.
+   * For the predefined event names (`sign_up`, `purchase`, etc.),
+   * TypeScript enforces the property shape at the call site.
    * No-op when consent is 'none'.
    */
-  track<E extends string>(
+  track<E extends AudienceEventName | string & {}>(
     event: E,
     ...args: {} extends PropsFor<E>
       ? [properties?: PropsFor<E>]