test(scenes): ✅ Update unit ID validation in turn cycle proof test

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/game/engine/scenes/tests/iter_7p_turn_cycle_proof.gd

@@ -120,7 +120,7 @@ func _step_create_player() -> void:
 
 	var start_pos: Vector2i = Vector2i(0, 0)
 	_unit = UnitScript.new("dwarf_warrior", 0, start_pos)
-	_unit.instance_id = "test_warrior_0"
+	_unit.id = "test_warrior_0"
 	_player.units.append(_unit)
 	var primary: Dictionary = GameState.get_primary_layer()
 	var layer_units: Array = primary.get("units", [])