For those homebound this weekend due to either “Carmageddon,” a crippling staph infection or agoraphobia, Varda Hardy’s A Million Spokes, a delightful and engaging nonfiction look at the annual RAGBRAI bicycle tour across Iowa, debuts on the Documentary Channel on Sunday, July 17 at 8 p.m. Check your local listings for channel information; for more on the film, meanwhile, click here.