“Mostly, I get to go past the velvet ropes,” is how Jane Pauley describes her role hosting CBS Sunday Morning ’s annual design episode. Recently, that all-access pass took her to Philadelphia and its remarkable design destinations. One was Ardrossan , the 38,000-square-foot Gilded Age mansion—still to this day a private home—that inspired the classic film The Philadelphia Story . Another was Chanticleer , a 48-acre pleasure garden established on the Main Line a century ago. Both are featured in this year’s “By Design,” episode airing May 17, which is anchored in the city in honor of the country’s 250th anniversary. Jane Pauley with her Today Show colleagues in 1982 NBC NewsWire/Getty Images It’s Pauley’s ninth year hosting the special, though American audiences have been watching the broadcaster for over five decades. She spent thirteen years as a cohost of the Today Show and has been a contributing anchor at CBS News since 2014.…