Rookie inside linebacker Reuben Foster was moving around the locker room without his walking boot or a noticeable limp Tuesday, nine days after he sustained a high ankle sprain in the season opener. That’s an encouraging sign for the 49ers, who have been replacing Foster with Ray-Ray Armstrong and, briefly, Brock Coyle. Foster won’t be available for Thursday’s game against the Rams, and defensive coordinator Robert Saleh indicated Coyle could play more in his absence.