IN A RENTED warehouse in the Seattle suburbs, Nordstrom Inc. executives have built a life-size mock-up of each floor of their latest men’s department store. It is furnished with a blend of actual shelving and dummy plywood tables, creating a surreal retail theater 45 minutes from Nordstrom’s downtown headquarters. The real thing is set to open in New York City in April, on Broadway between 57th and 58th streets.