NEW YORK — Thousands of New York City transit workers flooded lower Manhattan after the Sept. 11 attacks, lending crucial hands and expertise in the city’s greatest hour of need. More than two decades later, they want their due. Officials at Transport Workers Union Local 100 — which represents roughly half of the Metropolitan Transportation Authority’s workforce — are angered by what they consider a lack of representation for their members at the downtown National September 11 Memorial Museum. Transit workers who spent months clearing rubble, rebuilding tracks and driving buses near ground zer...