Delete Async Chat Stream

Delete an asynchronous chat stream and clean up all associated resources. This endpoint permanently removes a chat stream from storage and cleans up all associated resources including: - Stream metadata and status information - Cached events and message content - Task references and cancellation tokens Notes: - Stream must exist to be deleted (returns 404 otherwise) - Active streams are automatically cancelled before deletion - No response body returned on successful deletion (204 status) - Use status endpoint to verify deletion if needed