scripts: name the desktop setup for what it installs

Section 17 was still labelled "XFCE + VNC" while the step it runs installs
ubuntu-desktop and is guarded on it, so the heading described a setup the
script had already stopped producing.

Also spell out why setup-desktop.sh disables lightdm: it is not a display
manager this script ever installs, it is residue on hosts set up by an earlier
version that did install XFCE, and left enabled it beats GDM to the seat.

Comments and one echo string; no behaviour change.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup-desktop.sh

@@ -56,7 +56,8 @@ echo "[3/6] Setting GDM as the default display manager..."
 echo "/usr/sbin/gdm3" | sudo tee /etc/X11/default-display-manager > /dev/null
 sudo systemctl enable gdm3 >/dev/null 2>&1 || sudo systemctl enable gdm >/dev/null 2>&1 || true
 sudo systemctl set-default graphical.target >/dev/null 2>&1 || true
-# Disable any prior display manager (e.g. lightdm from an XFCE setup) so it doesn't fight GDM.
+# Disable any prior display manager so it doesn't fight GDM. lightdm is named because earlier versions
+# of this script installed XFCE; a host set up back then still has it and it would win the boot race.
 sudo systemctl disable lightdm >/dev/null 2>&1 || true
 echo "  Done (takes effect on next reboot)."
 

scripts/setup.sh

@@ -862,9 +862,9 @@ ENVFILE
   ok ".env written to $PROJECT_DIR/.env"
 fi
 
-# ─── 17. remote desktop (XFCE + VNC) ────────────────────────────────────────
+# ─── 17. remote desktop (Ubuntu Desktop + VNC) ───────────────────────────────
 echo ""
-echo "── Remote Desktop (XFCE + VNC) ──"
+echo "── Remote Desktop (Ubuntu Desktop + VNC) ──"
 
 if dpkg -s ubuntu-desktop &>/dev/null 2>&1; then
   skip "remote desktop (ubuntu-desktop already installed)"