The first plan to manage roughly 250 miles of road and trails in Marin’s open space preserves, and its environmental impact report, were approved by county supervisors on Tuesday after years of local input and pushback on restrictions in earlier iterations. Supervisors made a few final tweaks to the plan this week, including allowing dogs to remain off-leash in the Gary Giacomini Preserve in the San Geronimo Valley and requiring monitoring when the open space…