By Tom Verducci Houston and Dusty Baker have won their title, thoroughly and convincingly. Three hours before a game 25 years and a thousand heartaches in the making, and with fresh news that his first baseman is out with a knee injury, Astros manager Dusty Baker relaxes in his office to the plaintive wails of the Texas blues, courtesy of Big Mama Thornton. Like Baker, Big Mama came to Houston to find unprecedented success. This was to be the third time Baker sat in his managerial office with a chance to win the World Series that night. The other two, both in 2002, ended in disaster. In Game 6…