By Stephanie Apstein He was traded to Houston to add some thump to the lineup. Instead, his signature moment came on defense. PHILADELPHIA — In the 32 days since he last had a hit, Trey Mancini has had a lot of time to visualize how he might contribute to his team’s World Series run. Maybe he would start at designated hitter and sting a line drive into the gap. Maybe he would enter as a pinch hitter and loft a ball over the wall. Maybe he would beat out an infield single. Anything, really, to feel like he had made an impact on an Astros team that traded for him expecting one. Instead, as he st…