Full-frame updates send ABGR instead of BGRA #6

Hey — there’s a byte-order/alpha bug in tinyturing/display.py.

Pixels are stored as 0xRRGGBB00, so .tobytes() sends 00 B G R on little-endian machines. Rev C full frames expect opaque BGRA: B G R FF. Partial updates are fine because they explicitly send BGR.

On a 5" Red v2 this made white yellow and pure red/green/blue black. Confirmed with an eight-color test grid.

This fixes both full-refresh paths:

-framebuffer = self.framebuffer.transpose().tobytes()
+framebuffer = ((self.framebuffer.transpose() >> 8) | np.uint32(0xff000000)).tobytes()