Ryan Adams is a frustratingly fake pop star. His prodigious talent, heartfelt ambition and witty charm make him alluring to anyone who can appreciate good old-fashioned classic rock songwriting. An erratic musical chameleon, Adams, 29, has already fronted an acclaimed alt-country-defining band with Whiskeytown and released a slew of solo albums. After his solo debut, 2000’s melancholy masterpiece “Heartbreaker,” and its epic follow-up, 2001’s ode to ’70’s rock “Gold,” I believed Adams was the next great singer/songwriter. But then came 2002’s “Demolition.” The record was not his “official” third album but a collection of songs he had amassed over the preceding few years. Littered with clich