ROMULUS, Mich. — Jim Harbaugh returned Thursday night from southern California no longer in his Michigan maize and blue but wearing a powder blue sweater with a sunshine gold Los Angeles Chargers lightning bolt. Harbaugh made his way into the terminal at Detroit Metro Airport, fans occasionally stopping to ask for a photo with him, to congratulate him on Michigan’s national championship or to wish him well in his new role as the Chargers head coach. After nine seasons as head coach of the Wolverines, Harbaugh, 60, officially became the Chargers’ coach on Wednesday, 16 days after he led Michiga…