U.S. stocks are on pace for their worst performance in a November since 2008, while global investors are bullish at a level that hasn’t been seen in more than a decade. The contrarian signals sum up the challenging backdrop investors face heading into the final weeks of the year, with Nvidia earnings on Wednesday likely to define performance in a market beset with concerns over the pace of artificial-intelligence investments and the stretched valuations of the world’s biggest tech stocks. The has fallen more than 2.4% for the month, paced by declines in megacap tech stocks, and closed below its 50-day moving average, a key performance benchmark, for the first time on Monday since April...