SEOUL, South Korea — Chinese President Xi Jinping and North Korean leader Kim Jong Un underscored their commitment to deepen cooperation in a closely watched summit on Monday, as Xi made a rare visit to Pyongyang in a likely attempt to reassert Beijing’s unique influence over its socialist neighbor. It’s Xi’s first visit to North Korea in seven years. Earlier Monday, he was given a lavish welcome upon arrival at Pyongyang’s international airport. He and his wife Peng Liyuan were greeted by Kim