Ruhollah Habibi dresses sharply in a suit and tie each morning for his job at JP Morgan. But the banker also carries a thobe to work on Fridays, slipping on the Arabian-style tunic for afternoon prayers. "I just take off my suitcoat and throw that on over my button-up," said the 28-year-old San Ramon resident. "It's our etiquette to wear Islamic clothing when you're going to learn the sacred knowledge." From kufi caps to veils and ankle-length abayas, multicultural Muslim clothing is in demand among the Bay Area's young and devout. American-born Muslims who once shunned their immigrant parents' Old...