When asked to describe her male clients’ wardrobes, Sarah Gilfillan lists chinos, shades of navy, gray, black and white—and “loads” of overshirts, the shirtjacket hybrids. “Nearly everyone’s dressing casually now,” said the…

When asked to describe her male clients’ wardrobes, Sarah Gilfillan lists chinos, shades of navy, gray, black and white—and “loads” of overshirts, the shirtjacket hybrids. “Nearly everyone’s dressing casually now,” said the…