As of midnight Tuesday, all of CVS’s 7,700 stores are tobacco-free zones.The move fulfills a pledge the company made in February. Indeed, the chain now operates under the name CVS Health, symbolizing its strategy to become a health-care destination. The company already operates 900 walk-in clinics. Pharmacies across the U.S. are repositioning themselves to prosper in the burgeoning health-care industry. Customers accustomed to popping into CVS stores to grab a pack of cigarettes will now find only products designed to help them quit.