Know something about antiques? Prove it,” screamed the ad seeking “pickers” for Market Warriors, the long-awaited companion series to PBS’s most popular primetime program, Antiques Roadshow. Though PBS pioneered the concept of reality television with American Family and other cinema verité documentary series, it refrained from adding more reality TV as the genre became a staple of commercial television. But with the coming summer season and beyond, PBS is dipping into the reality game. A trio of unscripted programs — each coproduced by Boston’s WGBH— will premiere within the next year.