I’m missing the point, why do you want to use one length of wire for each row and column.
As you are going to solder the joints anyway and the led legs will be bent in different directions why not just use ordinary multi strand hook up wire cut to short lengths and solder them at the legs of the leds.
Ok so you have two wire ends to solder to each leg, and with 1296 leds that’s a lot of joints, but the spacing is uniform and you could cut, strip and tin the ends of the wires beforehand, once done the attaching to the led legs would be quick and easy just tedious as there are so many.