Bring back gl acceleration for the test VM

Ported from omarchy-4 (764a65f), including that branch's follow-up
switch from GTK to SDL: GTK's GL display path crops the guest
framebuffer on HiDPI Wayland desktops (434db24).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bin/omarchy-iso-boot

@@ -53,8 +53,8 @@ qemu-system-x86_64 \
   -device virtio-blk-pci,drive=drive0,bootindex=1 \
   -drive file="$ISO",media=cdrom,if=none,format=raw,id=cdrom0 \
   -device ide-cd,drive=cdrom0,bootindex=2 \
-  -device virtio-vga \
-  -display gtk \
+  -device virtio-vga-gl \
+  -display sdl,gl=on \
   -usb -device usb-tablet \
   -netdev user,id=net0,hostfwd=tcp::2222-:22 \
   -device virtio-net-pci,netdev=net0 \