A bruising global tech rout slammed markets Tuesday after South Korea's chip-heavy KOSPI index crashed 9.99% — meeting the technical definition of a correction — and the contagion swept across Europe into the United States. The Nasdaq Composite plunged 580 points (2.2%) to close at 25,587, the S&P 500 fell 1.4% to 7,365, and the Dow managed to escape with just a 0.1% dip. The trigger: investors asking whether the trillion-dollar AI...