The 49ers are going all-in for a Robert Saleh reunion. The former New York Jets head coach has an offer on the table from San Francisco to become the highest-paid defensive coordinator in the NFL, according to The Athletic’s Matt Barrows. “I think it’s become obvious now that it’s Saleh or bust really, because [the 49ers] haven’t done much work with anybody else to this point,” Barrows said on the “49ers +/-” podcast with Tim Kawakami. “And I’ve…