DETROIT — From Day One, Tigers president Scott Harris said he was more than willing to negotiate contract extensions for top prospects, if the club felt they were worthy. Tigers No. 2-ranked prospect Colt Keith is apparently worthy. The Tigers on Sunday signed Keith, a 22-year-old infielder who has yet to make his Major League debut, to a six-year contract extension running through 2029 worth $28.64 million. The deal includes team options through 2032 and bonuses that could take the contract’s value up to $82 million. “This is a very exciting day for the Detroit Tigers, Colt, his family, and o…