fix(live-iso): stop initrd GPU panic + clear install pointer on login

- boot.initrd.kernelModules force-loaded amdgpu+radeon+nouveau+i915 in the
  live ISO, panicking on hosts where more than one driver matched the GPU.
  Move them to availableKernelModules so udev only loads what fits.
- Override services.getty.helpLine with a Nomarchy welcome that points at
  `sudo /etc/install.sh` (+ --dry-run / --resume variants). Replaces the
  upstream "NixOS" message.
- Ship installer/hardware-db.sh as /etc/hardware-db.sh so the installer's
  auto-detection works when invoked from the live ISO.
- Add live-ISO-only Hyprland exec-once: notify-send + an alacritty
  "Nomarchy Installer" terminal that prints the install commands. The
  graphical autologin user now sees a pointer instead of guessing how to
  start the install.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

hosts/live-iso.nix

@@ -25,9 +25,16 @@
   users.users.nixos.extraGroups = [ "wheel" "video" "render" "audio" "networkmanager" ];
 
   # Graphics support for live environment.
-  # `virtio` is a no-op on real hardware (no virtio-gpu PCI device) but lets
-  # the ISO render correctly when booted in QEMU via nomarchy-test-live-iso.
-  boot.initrd.kernelModules = [ "amdgpu" "radeon" "nouveau" "i915" "virtio_gpu" ];
+  #
+  # Force-loading every GPU driver in the initrd (amdgpu+radeon+nouveau+i915)
+  # panics most machines — only one of them can claim the GPU and the others
+  # explode. List them under `availableKernelModules` instead so udev only
+  # loads the one that matches the present hardware. We still force the AMD
+  # pair when Plymouth needs KMS early; `virtio_gpu` is auto-loaded when
+  # we're booted in QEMU via nomarchy-test-live-iso.
+  boot.initrd.availableKernelModules = [
+    "amdgpu" "radeon" "nouveau" "i915" "virtio_gpu"
+  ];
   services.xserver.videoDrivers = [ "amdgpu" "radeon" "nouveau" "modesetting" "fbdev" "virtio" ];
 
   environment.etc."install.sh" = {
@@ -35,9 +42,28 @@
     mode = "0755";
   };
 
+  environment.etc."hardware-db.sh" = {
+    source = ../installer/hardware-db.sh;
+    mode = "0644";
+  };
+
   environment.etc."disko-golden.nix" = {
     source = ../installer/disko-golden.nix;
   };
 
   environment.etc."nomarchy".source = inputs.self;
+
+  # Override the upstream installer helpLine (says "NixOS", points nowhere
+  # useful for us). Shown on every TTY before login and again as the MOTD.
+  services.getty.helpLine = lib.mkForce ''
+
+    Welcome to the Nomarchy live environment.
+
+    To install Nomarchy:        sudo /etc/install.sh
+    To preview the install:     sudo /etc/install.sh --dry-run
+    To resume an interrupted run: sudo /etc/install.sh --resume
+
+    The graphical session autologins as 'nixos' (no password).
+    The 'nixos' and 'root' accounts have empty passwords.
+  '';
 }