Stocks opened mostly higher Thursday but lost momentum as the session wore on. A continued decline in several mega-cap stocks drove most of the day's price action, while earnings news captured the bulk of the headlines.   As for those earnings, Taiwan Semiconductor Manufacturing (TSM) reported higher-than-expected second-quarter top- and bottom-line results thanks to increased demand for its artificial intelligence (AI) chips. The semiconductor stock was choppy throughout the day, eventually ending with a m ...