U. S. stocks closed lower Friday as a pullback in big AI-focused companies weighed on the market, capping a turbulent week on Wall Street. The S&P 500 fell 0. 4%, but managed to post a 2. 5% gain for the week. This marks the benchmark index’s first winning week since October and its biggest weekly gain since August. The Dow Jones Industrial Average recovered from an early slide and eked out a 0. 1% gain. The Nasdaq composite fell 0. 9%, but also notched its first weekly gain in five weeks. a...