Two months after DeepSeek, China’s artificial intelligence star, rattled Washington and shook Wall Street, U.S. officials are taking steps to crack down on the Chinese start-up and its support from America’s leading chip maker, Nvidia.The Trump administration this week moved to restrict Nvidia’s sale of A.I. chips to China. It also is weighing penalties that would block DeepSeek from buying U.S. technology and debating barring Americans’ access to its services, said three people with knowledge of the action ...