Who knew that until the middle of the last century, East Granby, Connecticut, was a center for Connecticut Shade, a hand-tended tobacco leaf used as a wrapper for premium cigars? And that the work, which relied a lot on summer migrants, many students from the South, once included Martin Luther King? Keith Scribner knew because he spent a lot of time in East Granby when he was young, and he knows that growing and harvesting tobacco is a back-breaking chore. That he makes this dying industry the backdrop for a tale about generational domestic violence in his new book, “Old Newgate Road,” is inspired. It’s thirty years since Cole Callahan, an environmentally sensitive and successful architect, escaped from East Granby to the West Coast. As the novel opens, Cole, now 45, has returned to the Connecticut Valley to meet a colleague who’s arranging a shipment for him of American chestnut wood. He takes the occasion to drive to his former home on Old Newgate Road. The house is a white colonial