After several years of trying, a tech billionaire has finally won approval to rebuild a crumbling, 150-foot-long seawall that fronts his home overlooking Bolinas Beach. The wall will be narrower than the current structure but will include public benches and wheelchair access. At high tide, crossing over the seawall at the end of Brighton Avenue is the only way for visitors to get to the upcoast side of the beach. The wall, now more than…