fix: cosmic-greeter greeter chain in calamares; add vulkan-nouveau for NVK

- calamares: insert cosmic-greeter-start branch into DMgreetd.set_autologin
  (anchored on the ddlm elif) so COSMIC+greetd installs launch the correct
  greeter instead of falling back to agreety. pkgrel 7 -> 8.
- branding netinstall: add vulkan-nouveau so newer NVIDIA GPUs work via the
  open NVK stack without nvidia-open. pkgrel bump not needed (netinstall only).

packages/calamares-branding-antergos-next/netinstall.yaml

@@ -17,6 +17,7 @@
     - falkon
     - mesa
     - mesa-utils
+    - vulkan-nouveau
     - networkmanager
     - network-manager-applet
     - pipewire

packages/calamares/PKGBUILD

@@ -5,7 +5,7 @@
 _pkgname="calamares"
 pkgname="$_pkgname"
 pkgver=3.4.2
-pkgrel=7
+pkgrel=8
 pkgdesc="Distribution-independent installer framework"
 url="https://codeberg.org/Calamares/calamares"
 license=("GPL-3.0-or-later")
@@ -46,6 +46,11 @@ build() {
 
   local _pkgsrc_dir="$srcdir/$_pkgname-$pkgver"
 
+  sed -i '/"ddlm --target " + de_command/a\
+        elif os.path.exists(self.os_path("usr/bin/cosmic-greeter-start")):\
+            self.config_data["default_session"]["command"] = "cosmic-greeter-start"' \
+    "$_pkgsrc_dir/src/modules/displaymanager/main.py"
+
   local _cmake_options=(
     -B build
     -S "$_pkgsrc_dir"