Refactor pkgmgr installers, introduce capability-based execution, and replace manifest layer

References:
- Current ChatGPT conversation: https://chatgpt.com/share/6935d6d7-0ae4-800f-988a-44a50c17ba48
- Extended discussion: https://chatgpt.com/share/6935d734-fd84-800f-9755-290902b8cee8

Summary:
This commit performs a major cleanup and modernization of the installation pipeline:

1. Introduced a new capability-detection subsystem:
   - Capabilities (python-runtime, make-install, nix-flake) are detected per installer/layer.
   - Installers run only when they add new capabilities.
   - Prevents duplicated work such as Python installers running when Nix already provides the runtime.

2. Removed deprecated pkgmgr.yml manifest installer:
   - Dependency resolution is now delegated entirely to real package managers (Nix, pip, make, distro build tools).
   - Simplifies layering and avoids unnecessary recursion.

3. Reworked OS-specific installers:
   - Arch PKGBUILD now uses 'makepkg --syncdeps --cleanbuild --install --noconfirm'.
   - Debian installer now builds proper .deb packages via dpkg-buildpackage + installs them.
   - RPM installer now builds packages using rpmbuild and installs them via rpm.

4. Switched from remote GitHub flakes to local-flake execution:
   - Wrapper now executes: nix run /usr/lib/package-manager#pkgmgr
   - Avoids lock-file write attempts and improves reliability in CI.

5. Added bash -i based integration test:
   - Correctly sources ~/.bashrc and evaluates alias + venv activation.
   - ‘pkgmgr --help’ is now printed for debugging without failing tests.

6. Updated unit tests across all installers:
   - Removed references to manifest installer.
   - Adjusted expectations for new behaviors (makepkg, dpkg-buildpackage, rpmbuild).
   - Added capability subsystem tests.

7. Improved flake.nix packaging logic:
   - The entire project source tree is copied into the runtime closure.
   - pkgmgr wrapper now executes runpy inside the packaged directory.

Together, these changes create a predictable, layered, capability-driven installer pipeline with consistent behavior across Arch, Debian, RPM, Nix, and Python layers.

PKGBUILD

@@ -3,31 +3,72 @@
 pkgname=package-manager
 pkgver=0.1.1
 pkgrel=1
-pkgdesc="Wrapper that runs Kevin's package-manager via Nix flake."
+pkgdesc="Local-flake wrapper for Kevin's package-manager (Nix-based)."
 arch=('any')
 url="https://github.com/kevinveenbirkenbach/package-manager"
 license=('MIT')
 
+# Nix is the only runtime dependency; Python is provided by the Nix closure.
 depends=('nix')
+makedepends=('rsync')
 
 install=${pkgname}.install
 
-source=('scripts/pkgmgr-wrapper.sh'
-        'scripts/init-nix.sh')
-sha256sums=('SKIP'
-            'SKIP')
+# Local source checkout — avoids the tarball requirement.
+# This assumes you build the package from inside the main project repository.
+source=(
+  "scripts/pkgmgr-wrapper.sh"
+  "scripts/init-nix.sh"
+)
+
+sha256sums=('SKIP' 'SKIP')
+
+# Local source directory name under $srcdir
+_srcdir_name="source"
+
+prepare() {
+  mkdir -p "$srcdir/$_srcdir_name"
+
+  # Copy the full local tree into $srcdir/source,
+  # but avoid makepkg's own directories and the VCS metadata.
+  rsync -a \
+    --exclude="src" \
+    --exclude="pkg" \
+    --exclude=".git" \
+    "$startdir/" "$srcdir/$_srcdir_name/"
+}
 
 build() {
+  cd "$srcdir/$_srcdir_name"
   :
 }
 
 package() {
-  install -d "$pkgdir/usr/bin"
-  install -d "$pkgdir/usr/lib/package-manager"
+  cd "$srcdir/$_srcdir_name"
 
-  # Wrapper
-  install -m0755 "scripts/pkgmgr-wrapper.sh" "$pkgdir/usr/bin/pkgmgr"
+  # Install the wrapper into /usr/bin
+  install -Dm0755 "scripts/pkgmgr-wrapper.sh" \
+    "$pkgdir/usr/bin/pkgmgr"
 
-  # Shared Nix init script
-  install -m0755 "scripts/init-nix.sh" "$pkgdir/usr/lib/package-manager/init-nix.sh"
+  # Install Nix init helper
+  install -Dm0755 "scripts/init-nix.sh" \
+    "$pkgdir/usr/lib/package-manager/init-nix.sh"
+
+  # Install the full repository into /usr/lib/package-manager
+  mkdir -p "$pkgdir/usr/lib/package-manager"
+
+  # Copy entire project tree from our local source checkout
+  cp -a . "$pkgdir/usr/lib/package-manager/"
+
+  # Remove packaging-only and development artefacts from the installed tree
+  rm -rf \
+    "$pkgdir/usr/lib/package-manager/.git" \
+    "$pkgdir/usr/lib/package-manager/.github" \
+    "$pkgdir/usr/lib/package-manager/tests" \
+    "$pkgdir/usr/lib/package-manager/PKGBUILD" \
+    "$pkgdir/usr/lib/package-manager/Dockerfile" \
+    "$pkgdir/usr/lib/package-manager/debian" \
+    "$pkgdir/usr/lib/package-manager/.gitignore" \
+    "$pkgdir/usr/lib/package-manager/__pycache__" \
+    "$pkgdir/usr/lib/package-manager/.gitkeep"
 }