fedora-remote: add Mesa EGL for Proxmox virtio-gpu acceleration

base-atomic ships mesa-dri-drivers (the virtio_gpu Gallium driver) but not
mesa-libEGL, and with recommends off nothing pulls it in. mutter/gnome-shell
only require libglvnd's EGL dispatcher, which then has no Mesa backend, so the
session falls back to llvmpipe software rendering. Add mesa-libEGL explicitly
so the host iGPU is used under Proxmox's VirGL/virtio-gpu display.

images/fedora-remote/custom.yaml

@@ -23,6 +23,15 @@ packages:
   # Proxmox guest integration.
   - qemu-guest-agent
 
+  # Proxmox virtio-gpu display (VirGL): render on the host iGPU instead of
+  # software (llvmpipe). mesa-dri-drivers ships the virtio_gpu Gallium driver
+  # and comes from base-atomic; mesa-libEGL is the piece base-atomic lacks - it
+  # provides the Mesa EGL vendor, without which libglvnd's EGL dispatcher has no
+  # backend and mutter/gnome-shell fall back to software rendering. Listed
+  # explicitly (recommends are off) so the GL stack survives upstream changes.
+  - mesa-dri-drivers
+  - mesa-libEGL
+
   # grd-firstboot generates the RDP TLS certificate with the openssl CLI.
   - openssl