From Tom Dotan, our new senior correspondent, fresh off two years covering Microsoft for the Wall Street JournalAt Microsoft’s annual executive huddle last month, the company’s chief financial officer, Amy Hood, put up a slide that charted the number of users for its Copilot consumer AI tool over the past year. It was essentially a flat line, showing around 20 million weekly users.On the same slide was another line showing ChatGPT’s growth over the same period, arching ever upward toward 400 mil...