China’s top market regulator has summoned the country’s leading tech companies to demand an end to “involutionary” competition, at the time when the companies are pouring billions of yuan into a Lunar New Year promotional blitz to win over users for services including artificial intelligence apps. The companies summoned on Friday were Alibaba Group Holding, ByteDance’s Douyin, Baidu, Tencent Holdings, JD.com, Meituan and Taobao Instant Commerce, Alibaba’s on-demand delivery unit, the State...