Replace the in-render-window palette strips with three separate 640x480
windows, one per VDB display palette (secondary/aux1/aux2). Each has its own
GL context (rt_main wglMakeCurrent-s each per tick) and shows the palette as a
16x16 color grid, redrawn every 50ms so it animates live regardless of the VPX
render cadence. make_gl_window() factored out; strips + VPX_VDBSTRIP removed.
Confirmed live: aux1 = red/green/olive/black status checkerboard, aux2 = a
4-region color map (green/blue/red/purple, 64 entries each), secondary = the
animated one (black between flashes).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>