“Welcome home, Terrapin Nation,” Phil Lesh proclaimed on July 9 to the large crowd before him on the expansive, lush lawn of McNears Beach Park on the shores of San Pablo Bay in San Rafael, Calif. Lesh, co-founder of the Grateful Dead and now 83, joined the so-called Terrapin All-Stars for the closing set of a first-ever, one-day Sunday Daydream festival, which began in the early morning with an aptly named Turtle Trot that included 5K, 10K, and kids races.