BUNER, Pakistan Rescue workers in northwestern Pakistan expanded relief operations yesterday after flash floods killed more than 220 people in a single district, officials said. Buner, a mountainous district in Khyber Pakhtunkhwa province, was struck by cloudbursts and torrential monsoon downpours on Aug. 15, triggering flash floods and landslides. An emergency services spokesman in Buner, Mohammad Sohail, said more than half of the damaged roads in the district have been reopened, allowing