Shared Utilities (draw_util.c)

• probe_draw_quad(x, y, w, h, z, argb, list) — colored quad
• probe_draw_textured_quad(x, y, w, h, z, list) — textured quad
• probe_draw_text(x, y, str) — BIOS font overlay
• probe_draw_label(str) — bottom status bar
• probe_draw_split() — vertical center line
• probe_twiddle(w, h, src, dst) — correct Morton twiddle
• probe_twiddle_swapped(w, h, src, dst) — deliberately wrong twiddle