ON A RECENT Monday morning, Sandeep Salter walked quickly down Henry Street, rounded onto Atlantic Avenue, and pushed open the door to her shop Salter House. We wound past the marble café tables and the rows of horsehair brooms and frilly checked pillows and into the recent addition: a cozy extension to the store, opening November 7, out of which Salter will sell the clothes she designs. “I want this to feel like a bedroom,” she said, showing me where hanging racks will line one wall, stocked with loose cotton dresses and floral corsets and coats that fasten with a bow. She sat down on a sofa (parabolic, taupe, antique, French), lifted her feet (white socks, lace) out of her loafers (brown, suede, low heel), crossed her legs under her,…