Apple Inc. is planning to overhaul its Siri virtual assistant with more advanced artificial intelligence, a move that will let users control individual app functions with their voice, according to people with knowledge of the matter. The new system will allow Siri to take command of all the features within apps for the first time, said the people, who asked not to be identified because the initiative isn’t public. That change required a revamp of Siri’s underlying software using large language m...