Taylor Swift’s reimagined “1989” is here, the album that ushered in the first Peak Swift era — revisited at the height of her massive pop culture dominance. Swift had shed the Nashville country roots of her first four studio albums and announced herself a full-fledged pop superstar. “1989 (Taylor’s Version),” out Friday, takes that version of Swift — then in her mid-20s, living in New York, prepared to take on the world with an arsenal of ’80s synth sounds and a new producer named Jack Antonoff — and includes five unreleased “vault” tracks that deliver more clues about the artist she was then.