**Refactor Nix init into modular scripts and update packaging paths**

* Move the Nix bootstrap from *scripts/init-nix.sh* to *scripts/nix/init.sh* with split-out helpers in *scripts/nix/lib/*
* Update Arch/Debian/Fedora packaging hooks to call */usr/lib/package-manager/nix/init.sh*
* Keep bootstrap behavior the same while improving maintainability and reuse

https://chatgpt.com/share/693c7159-b340-800f-929e-2515eeb0dd03

packaging/arch/PKGBUILD

@@ -51,8 +51,8 @@ package() {
     "$pkgdir/usr/bin/pkgmgr"
 
   # Install Nix init helper
-  install -Dm0755 "scripts/init-nix.sh" \
-    "$pkgdir/usr/lib/package-manager/init-nix.sh"
+  install -Dm0755 "scripts/nix/init.sh" \
+    "$pkgdir/usr/lib/package-manager/nix/init.sh"
 
   # Install the full repository into /usr/lib/package-manager
   mkdir -p "$pkgdir/usr/lib/package-manager"

packaging/arch/package-manager.install

@@ -1,9 +1,9 @@
 post_install() {
-  /usr/lib/package-manager/init-nix.sh || echo ">>> ERROR: /usr/lib/package-manager/init-nix.sh not found or not executable."
+  /usr/lib/package-manager/nix/init.sh || echo ">>> ERROR: /usr/lib/package-manager/nix/init.sh not found or not executable."
 }
 
 post_upgrade() {
-  /usr/lib/package-manager/init-nix.sh || echo ">>> ERROR: /usr/lib/package-manager/init-nix.sh not found or not executable."
+  /usr/lib/package-manager/nix/init.sh || echo ">>> ERROR: /usr/lib/package-manager/nix/init.sh not found or not executable."
 }
 
 post_remove() {