Sonic Youth and their pet project (no pun intended) Be Your Own Pet played a day/night double header yesterday at the 9:30 Club that showcased two generations of bands on one stage. I was lucky enough to score tickets to the first show, which started around quarter ’til seven and was over before last night’s Mavs / Heat tilt tipped off. Despite seeing Sonic Youth numerous times over the years, mostly at fesitvals like…