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

debian/changelog

@@ -0,0 +1,5 @@
+package-manager (0.1.1-1) unstable; urgency=medium
+
+  * Initial release.
+
+ -- Kevin Veen-Birkenbach <info@veen.world>  Sat, 06 Dec 2025 16:30:00 +0100

debian/control

@@ -0,0 +1,18 @@
+Source: package-manager
+Section: utils
+Priority: optional
+Maintainer: Kevin Veen-Birkenbach <info@veen.world>
+Build-Depends: debhelper-compat (= 13)
+Standards-Version: 4.6.2
+Rules-Requires-Root: no
+Homepage: https://github.com/kevinveenbirkenbach/package-manager
+
+Package: package-manager
+Architecture: any
+Depends: nix, ${misc:Depends}
+Description: Wrapper that runs Kevin's package-manager via Nix flake
+ This package provides the `pkgmgr` command, which runs Kevin's package
+ manager via a Nix flake:
+   nix run "github:kevinveenbirkenbach/package-manager#pkgmgr" -- ...
+ Nix is used as the only runtime dependency and must be initialized on
+ the system to work correctly.

debian/postinst

@@ -0,0 +1,14 @@
+#!/bin/sh
+set -e
+
+case "$1" in
+    configure)
+        if [ -x /usr/lib/package-manager/init-nix.sh ]; then
+            /usr/lib/package-manager/init-nix.sh || true
+        else
+            echo ">>> Warning: /usr/lib/package-manager/init-nix.sh not found or not executable."
+        fi
+        ;;
+esac
+
+exit 0

debian/rules

@@ -0,0 +1,10 @@
+#!/usr/bin/make -f
+
+%:
+	dh $@
+
+override_dh_auto_install:
+	# Install wrapper
+	install -D -m0755 scripts/pkgmgr-wrapper.sh debian/package-manager/usr/bin/pkgmgr
+	# Install shared Nix init script
+	install -D -m0755 scripts/init-nix.sh debian/package-manager/usr/lib/package-manager/init-nix.sh