Chinese start-up DeepSeek recently displaced ChatGPT as the top-ranking artificial intelligence app, in part by dazzling the public with a free version of the hottest idea in AI — a chatbot that “thinks” before answering a user’s question.The app’s “DeepThink” mode responds to every query with the text, “Thinking…,” followed by a string of updates that read like the chatbot talking to itself as it figures out its final answer. The monologue unspools with folksy flourishes like, “Wait,” “Hmm,” or...