feat: vminstall.sh installs any boot loader and the Steamify ISO's Steamify step, with a package cache

VM_BOOTLOADER=limine|systemd-boot|grub, VM_STEAMIFY (steamify-install runs after
the headless installer, like Calamares does), VM_CACHE (host pacman cache shared
as 9p, default ~/vms/pkg-cache). run.sh --headless / VM_HEADLESS=1: no window.

Fixes found on the way: the live script deadlocked on is-system-running (it is
the running kernel-command-line.service) and now waits for pacman-init; the post
script kept forcing the Plasma login over Steamify's gaming-mode SDDM, gave
systemd-boot no timeout/default (it waited in the menu for ever), and left ufw
blocking the host's ssh; the first-boot check wanted plasmashell in gaming mode.

share/vminstall-post.sh

@@ -23,11 +23,18 @@ chmod 440 /etc/sudoers.d/99-test-vm
 
 # Log straight into Plasma (gamescope doesn't render in the VM). The
 # scripts expect plasma-login-manager, like a CachyOS install from Calamares.
-pacman -Q plasma-login-manager >/dev/null 2>&1 || pacman -S --needed --noconfirm plasma-login-manager
-systemctl disable sddm.service 2>/dev/null || true
-systemctl enable plasmalogin.service
-mkdir -p /etc/plasmalogin.conf.d
-printf '[Autologin]\nUser=%s\nSession=plasma.desktop\n' "$VM_USER" > /etc/plasmalogin.conf.d/00-test-autologin.conf
+# Not when Steamify's conversion is on (steamify-install ran on a Steamify
+# ISO): it made SDDM boot into gamescope, and that is what gets tested; sshd
+# doesn't need a desktop.
+if [[ -f /etc/sddm.conf.d/10-gamescope-autologin.conf ]]; then
+    echo "Steamify's gaming-mode login (SDDM) kept."
+else
+    pacman -Q plasma-login-manager >/dev/null 2>&1 || pacman -S --needed --noconfirm plasma-login-manager
+    systemctl disable sddm.service 2>/dev/null || true
+    systemctl enable plasmalogin.service
+    mkdir -p /etc/plasmalogin.conf.d
+    printf '[Autologin]\nUser=%s\nSession=plasma.desktop\n' "$VM_USER" > /etc/plasmalogin.conf.d/00-test-autologin.conf
+fi
 
 # cachyos-installer's limine.conf has no default_entry: entry 1 is the
 # "CachyOS" folder, so the first boot waits in the menu. 2 is its first
@@ -36,6 +43,19 @@ if [[ -f /boot/limine.conf ]] && ! grep -q '^default_entry:' /boot/limine.conf;
     sed -i 's/^timeout: .*/&\ndefault_entry: 2/' /boot/limine.conf
 fi
 
+# cachyos-installer's systemd-boot loader.conf has `#timeout 3` commented out and
+# no default: the first boot would wait in the menu for ever. Boot the first
+# kernel after 3 s.
+if [[ -f /boot/loader/loader.conf ]] && ! grep -q '^timeout' /boot/loader/loader.conf; then
+    printf 'timeout 3\ndefault linux-cachyos.conf\n' >> /boot/loader/loader.conf
+fi
+
+# The installer enables ufw, which drops the host's ssh connections (found
+# in the kernel log: [UFW BLOCK] DPT=22). Let ssh in; the rest stays as installed.
+if command -v ufw >/dev/null; then
+    ufw allow 22/tcp || echo "(ufw rule failed: ssh may be blocked)"
+fi
+
 # English everywhere, whatever the live ISO picked.
 echo 'LANG=en_US.UTF-8' > /etc/locale.conf