Slovakia rallied to beat Britain 2-1 and reach its first Billie Jean King Cup final in more than two decades on Tuesday. Viktoria Hruncakova and Tereza Mihalikova defeated Olivia Nicholls and Heather Watson 6-2, 6-2 in the decisive doubles match, putting Slovakia back in the final for the first time since 2002 to face last year’s runner-up Italy on Wednesday.