Kumar Arya, a City of Houston engineer, was summoned to his department's downtown offices last summer to defend his rejection of a Metro site plan. He didn't think the design would work.Leaving the meeting, Arya decided to ride the Metro rail back to his office at 3300 Main St. He says he stepped off the train, was grabbed from behind and thrown to the ground, then the assailant ripped off some jewelry Arya was wearing. He was injured - a broken nose and cut-up face, with lacerations severe enou