It feels too early to draw a bright pink line through Billie Eilish’s recording career, but do we really have a choice? Her obliterating ballad from last summer’s “Barbie” soundtrack, “What Was I Made For?,” felt so delicately inventive and deeply existential that it automatically split her songbook into before-and-after. So into the post-pink we go with “Hit Me Hard and Soft,” a new album that finds Eilish singing in exponentially more exquisite detail, making her melodized whispers work like steamrollers, roller coasters, pneumatic jackhammers, bombs bursting in air, hard and soft for real.