Create, retrieve, and update Chat assets through the Digital Asset API. Chat assets use the Mobile & Web app channel (channel=app) configured for Live Chat/In-App real-time messaging across Android, iOS, and Web, with JWT-based SDK authorization and Firebase-backed push. This spec was derived from the generic Mobile & Web app-channel spec (digital-api-spec-app-test.json) and validated end-to-end by capturing a live, successful "Create asset" flow from the Control Hub UI (Digital Channels > Assets > Create asset > Channel: Chat). Credential-bearing examples are sanitized for developer-portal publication.