In Mexico, officials and citizens routinely announce the discoveries of clandestine graves baring skeletal remains from the gang violence that has convulsed the country for years.The official count of the “disappeared” nationwide exceeds 30,000, and relatives of the legions of missing call that a low-ball estimate.But the macabre saga of a roving government-contracted truck ferrying the corpses of scores of apparent murder victims from one town to the next in western Jalisco state has added a bizarre new twist to Mexico’s violent narrative.The episode has become a . . .