A 39-foot female gray whale was found floating in the surf off Limantour Beach on Saturday, the first whale to wash ashore in the Bay Area this year. A team from the Marine Mammal Center and the California Academy of Sciences performed a partial necropsy at low tide on Saturday, with plans to return this week to collect more samples. But evidence so far points to death from malnutrition, said Dr. Padraig Duignan, director of…