MIAMI — More than 30 minutes after the final buzzer sounded, Jaylen Brown took a seat at his locker. He had just taken a shower, and was only in a towel. The Celtics All-Star was still trying to process what had just happened. He sat there, staring into the abyss. He shook his head, still in frustration. Moments later, he picked himself up, got dressed and took the walk to the visitors’ podium…