Coming down off the busy Thanksgiving weekend, this week’s box-office matchup was a contest of endurance. Tangled, Disney’s animated Rapunzel tale, held up best, dropping 56 percent from its debut to take in $21.5 million and land at No. 1. Harry Potter and the Deathly Hallows, which ruled the roost last week, tumbled a steeper 66 percent, ending up in second. Its domestic total now stands at $244 million, representing a speedier decline than any of the last three installments. Meanwhile, Natalie Portman’s buzzy ballerina film, Black Swan, took in an impressive $1.4 million from just 18 theaters.