Investors hoping for traditional holiday cheer for the ‌U.S. ​stock market are encountering turbulence that could keep markets ‌on edge into year-end. Despite stock indexes remaining on track for solid performance in 2025, the benchmark S&P 500 has ​edged lower so far in December, bucking historical trends that have shown it to be a strong month on average. Two themes have sparked swings in U.S. equities in recent weeks: ‍Scrutiny on massive corporate spending for the artificial ​intelligence...