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

