Josh Hartnett made his romance with Abbie Cornish public at a private dinner Saturday at Macao Trading Co. on Church Street. Hollywood’s newest couple helped Channing Tatum celebrate his 30th birthday hosted by artist and Dactyl founder Neil Grayson. A spy reports, “They turned up after midnight . . . they definitely looked like a couple.” Other guests included Tatum’s beautiful actress wife, Jenna Dewan; Hayley Duff with her actor boyfriend, Nick Zano; and Tatum’s “Son of No One” co-stars James Ransone and Ray Liotta.