SAN ANTONIO — A week of mystery ended with Mitchell Robinson on the court. But no more clarity on how he actually sustained his injury. Robinson played 13 minutes in the Knicks’ 105-95 Game 1 win over the Spurs on Wednesday night at Frost Bank Center. He recorded two points and six rebounds. His two points came on an alley-oop over Luke Kornet. “I didn’t think he was,” coach Mike Brown said when asked if he thought Robinson was limited. “I’ve got to go back and watch the tape. He caught a lob.