Chloé Zhao emerges from her cave — her words, not mine — with “ Hamnet .” It’s a film that feels less like a period drama and more like a spiritual excavation. The co-writer and director, who spent a decade traversing America for her first three features before winning an Oscar for “Nomadland” (2020), has created something that operates on a frequency beyond traditional narrative filmmaking. It’s a dangerous kind of vulnerability, and Zhao knows it. “We’re experiencing our tools to bring us to