At the beginning of the documentary "Jeremiah Tower: The Last Magnificent," which opens in the Valley Friday at Harkins Shea, the handsome old title character pads around what appear to be ancient Mexican ruins with a funereal look on his face, morosely contemplating the failure of the world to live up to his standards of perfection. But Tower is not a disillusioned political or religious idealist, not a diplomat whose plans for world peace have been ignored.