A rare bird has landed at the University of Michigan: a two-legged robot named “Cassie” that researchers hope could be the forerunner of a machine that one day will aid search-and-rescue efforts. Cassie—whose name is derived from the cassowary (KASS’-uh-WAIR’-ee), a flightless bird similar to an ostrich—stands upright on legs with backward-facing knees. The biped…