Add cross-distribution OS package installers (Arch PKGBUILD, Debian control, RPM spec) and restructure tests.

Remove deprecated AUR and Ansible requirements installers.
Introduce Nix init + wrapper scripts and full packaging (Arch/DEB/RPM).
Associated conversation: https://chatgpt.com/share/693476a8-b9f0-800f-8e0c-ea5151295ce2

scripts/init-nix.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo ">>> Initializing Nix environment for package-manager..."
+
+# 1. /nix Store
+if [ ! -d /nix ]; then
+  echo ">>> Creating /nix store directory"
+  mkdir -m 0755 /nix
+  chown root:root /nix
+fi
+
+# 2. nix-daemon aktivieren, falls vorhanden
+if command -v systemctl >/dev/null 2>&1 && systemctl list-unit-files | grep -q nix-daemon.service; then
+  echo ">>> Enabling nix-daemon.service"
+  systemctl enable --now nix-daemon.service 2>/dev/null || true
+else
+  echo ">>> Warning: nix-daemon.service not found or systemctl not available."
+fi
+
+# 3. Gruppe nix-users sicherstellen
+if ! getent group nix-users >/dev/null 2>&1; then
+  echo ">>> Creating nix-users group"
+  # Debian/RPM/Arch haben alle groupadd
+  groupadd -r nix-users 2>/dev/null || true
+fi
+
+# 4. Benutzer zu nix-users hinzufügen (Best-Effort)
+
+# a) Wenn loginctl vorhanden ist → alle eingeloggten User
+if command -v loginctl >/dev/null 2>&1; then
+  for user in $(loginctl list-users | awk 'NR>1 {print $2}'); do
+    if id "$user" >/dev/null 2>&1; then
+      echo ">>> Adding user '$user' to nix-users"
+      usermod -aG nix-users "$user" 2>/dev/null || true
+    fi
+  done
+# b) Fallback: logname (typisch bei Debian)
+elif command -v logname >/dev/null 2>&1; then
+  USERNAME="$(logname 2>/dev/null || true)"
+  if [ -n "$USERNAME" ] && id "$USERNAME" >/dev/null 2>&1; then
+    echo ">>> Adding user '$USERNAME' to nix-users"
+    usermod -aG nix-users "$USERNAME" 2>/dev/null || true
+  fi
+fi
+
+echo ">>> Nix initialization for package-manager complete."
+echo ">>> You may need to log out and log back in to activate group membership."

scripts/pkgmgr-wrapper.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Enable flakes if not already configured.
+if [[ -z "${NIX_CONFIG:-}" ]]; then
+  export NIX_CONFIG="experimental-features = nix-command flakes"
+fi
+
+# Run Kevin’s package manager via Nix flake
+exec nix run "github:kevinveenbirkenbach/package-manager#pkgmgr" -- "$@"