SAN JOSE — Arizona basketball has enjoyed a half-century of near-continuous men’s hoops excellence. The Wildcats have had 40 20-win seasons since 1975, with five different coaches contributing to that number. The last losing season was in 1983–84.One of the key elements of that sustained success has been a poach-proof array of coaches. If the university wanted to keep its guys, it has.Fred Snowden, who took Arizona to the 1976 NCAA tournament Elite Eight, did not coach again after a decade at the school. Lute Olson, the program patriarch, retired in 2007 after 24 years and a national championship. Sean Miller was fired in 2012, but spent 12 seasons at Arizona and might have stayed forever if not for that pesky FBI investigation of corruption in the sport.Now there is Tommy Lloyd, the best Wildcats coach since Olson, leading a wagon of a No. 1 seed into the West Regional final Saturday against Purdue.…