refactor(audience): dedup with core and remove sdk consent layer

- Delete web/src/attribution.ts, web/src/cookie.ts — use core's
  collectAttribution() and getOrCreateSession() instead
- Delete sdk/src/consent.ts, web/src/consent-transport.ts — use core's
  createConsentManager() instead of custom ConsentController class
- Web-specific cleanup (stop queue, delete cookies, purge identify/alias)
  now lives inline in ImmutableWebSDK.setConsent()

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

Author: ImmutableJeffrey

packages/audience/sdk/src/consent.test.ts

@@ -1,4 +1,2 @@
 export type { AudienceSDKConfig } from './types';
 export { DebugLogger } from './debug';
-export { ConsentManager } from './consent';
-export type { ConsentTransport, ConsentCallbacks } from './consent';