When Richard Hambleton died late last month, he was hailed as a founding father of street art, the man who’d made the world safe for Banksy. From a PR standpoint, his exit couldn’t have been better timed. After years lost to illness and addiction, over the past decade he’d reemerged into the spotlight. The street art renaissance secured him splashy gallery shows and the sponsorship of Giorgio Armani. A documentary about his life, Shadowman, debuted at the Tribeca Film Festival in April. His work…