As the Giants made their way into the first-base dugout at Sutter Health Park on Friday evening, a remnant from the previous night remained hung on the wall near the helmet rack: The lineup card of the Triple-A Reno Aces, who had just played the Sacramento River Cats. It was one of many reminders that the Giants and Athletics were playing a major league game in a minor-league stadium — that the Battle of the Bay was relegated to the past. “It felt a little different coming here today,” said manager Bob Melvin, who managed the Oakland A’s from 2011-21. Certainly last year in Oakland, the rivalry is pretty significant.