SEOUL — 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 and his wife Ri Sol Ju, who broadly smiled and clapped. Xi later arrived at Pyongyang’s main square, where a military...