Baidu enjoyed a headstart in China’s AI race but it soon lost its lead to rivals including ByteDance and Alibaba. Photographer: Na Bian/BloombergBaidu Inc. posted its biggest quarterly revenue slide on record, calling into question a beleaguered advertising business while it tries to keep up in the artificial intelligence race.Revenue declined 7% to 31.2 billion yuan ($4.4 billion) for the quarter ended September, compared with the average projection for 30.9 billion yuan. It swung to a net loss...