By Charlotte Graham-mclay WELLINGTON, New Zealand (AP) — It’s often a day marked by spirited politics and at times boisterous protest. But Thursday’s anniversary of New Zealand’s founding document, the Treaty of Waitangi, passed in muted fashion with Prime Minister Christopher Luxon absent from the main commemorations, amid rancor over an unpopular proposed law redefining the treaty’s promises. On Feb. 6 1840, representatives of the British Crown and 500 Māori tribal leaders signed a treaty at Waitangi, in New Zealand’s far north, agreeing to the terms of their relationship. In modern times, annual events attended by lawmakers and Indigenous leaders at the treaty grounds have allowed the groups to speak face to face, even at times of racial discord. It has also supplied a litmus test for governments and Māori…