<p>With a strict no-phones policy, a heap of ethereal indie-folk-rock cuts and a set design that could convince someone they had an encounter of the third kind, singer-songwriter Phoebe Bridgers took fans off the grid for an emotional stop on her headlining arena tour at the United Center on Saturday.</p><p>Bridgers held court on two stages, one anchored by her nine-piece band, and the other mostly reserved for more stripped-down arrangements. A gulf of adoring fans separated the two raised plat