MANCHESTER, England — Vincent Kompany’s thumping header gave Manchester City a crucial 1-0 derby win against Manchester United on Monday to overtake its rival atop the Premier League with just two games remaining. In what had been billed as the biggest Manchester derby ever, Kompany connected with David Silva’s corner to score the decisive goal in first-half stoppage time at the Etihad Stadium. City then held on for a potentially title-deciding victory as it now leads United on goal difference and once again has matters in its own hands, having erased an eight-point deficit in a couple of weeks. “Absolutely buzzing. … We’ve been waiting for this moment,” Kompany said. “It’s far from over, and we know that, but just to give our fans two wins over Manchester United this season — we have to finish it off.” City still has a tough job to do as it next visits fifth-place Newcastle United and then hosts relegation-threatened Queens Park Rangers in the remaining fixtures, while United finishes against Swansea at home and Sunderland away. “It’s great to win tonight, but Newcastle is now our focus,” City goalkeeper Joe Hart said. After leading the Premier League for most of the season,…