FORT MEADE, Md.—A military jury imposed a sentence of 26 years Friday on a former Maryland man who admitted joining the al-Qaida terrorist group and has been held at the Guantanamo Bay detention center. But under a plea deal, the man could be released as soon as next year because of his cooperation with U.S. authorities. The sentencing of Majid Khan is the culmination of the first trial by military commission for one of the 14 so-called high-value detainees who were sent to the U.S. naval base in Cuba in 2006 after being held in a clandestine network of overseas CIA detention facilities and subjected to the harsh interrogation program developed in response to the 9/11 attacks. Khan, a 41-year-old citizen of Pakistan who came to the United States in the 1990s and graduated from high school near Baltimore, earlier pleaded guilty to war crimes charges that included conspiracy and …