PHILADELPHIA — The most telling moment of James Harden’s introductory press conference with the 76ers came less than a minute in, with Josh Harris – the franchise’s principal owner – laying bare the power dynamic that defines the modern NBA and that will define Harden’s tenure with the team, however long it lasts. “James,” Harris said, glancing to his right toward Harden, “thank you for choosing Philly to play.” That’s what Tuesday afternoon’s gathering in Camden, N.J., was: an acknowledgment, and for Harris and the others on the dais, a celebration of Harden’s decision to grant the Sixers per…