An Oakland couple’s retroactive permit for a private trail they built from a second home in Seahaven to the shores of Tomales Bay was nullified last Friday when the California Coastal Commission found merit in an appeal against it. The Environmental Action Committee of West Marin appealed the county’s April approval of Peter Rumsey and Anna Edmondson’s 261-foot trail, which descends about 85 feet, includes a staircase that extends down the bluff face and ends…