The Federal Trade Commission proposed a rule Thursday that would ban U.S. employers from imposing noncompete clauses on workers, a sweeping measure that could make it easier for people to switch jobs and deepen competition for labor across a wide range of industries.The proposed rule would prevent employers from imposing contract clauses that prohibit their employees from joining a competitor, typically for a period of time, after they leave the company.Advocates of the new rule argue that noncompete agreements contribute …