A frenzy over an artificial intelligence chatbot made by Chinese tech startup DeepSeek was upending stock markets Monday and fueling debates over the economic and geopolitical competition between the U.S. and China in developing AI technology. DeepSeek's AI assistant became the No. 1 downloaded free app on Apple's iPhone store Monday, propelled by curiosity about the ChatGPT competitor. Part of what's worrying some U.S. tech industry observers is the idea that the Chinese startup has caught up with the American companies at the forefront of generative AI at a fraction of the cost. That, if true, calls into question the...