Tokyo stocks opened nearly flat Monday as bargain-hunting following the Nikkei index’s steep fall in the previous session was offset by caution ahead of congressional testimony by U.S. Federal Reserve Chairman Jerome Powell later this week. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 7.90 points, or 0.03 percent, from Friday to 25,970.90. The broader Topix index was up 0.56 points, or 0.03 percent, at 1,836.46. On the top-tier Prime Market, gainers were led by air transportation and transportation equipment issues, while mining, and oil and coal product issues l…