Restructure repo layout, wiring src/ and packaging for local and distro builds

- Add dev runner main.py that prefers local src/ over installed pkgmgr
- Move Arch/Debian/Fedora packaging files under packaging/* and update build scripts
- Adjust .gitignore/.dockerignore for new packaging paths and src/source/
- Improve config defaults discovery to support src/ layout and installed packages
- Update architecture diagram and add TODO overview for TAGS/MIRROR/SIGNING_KEY

https://chatgpt.com/share/693a76a0-e408-800f-9939-868524cbef4d

packaging/arch/PKGBUILD

@@ -0,0 +1,68 @@
+# Maintainer: Kevin Veen-Birkenbach <info@veen.world>
+
+pkgname=package-manager
+pkgver=0.9.1
+pkgrel=1
+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
+
+# Local source checkout — avoids the tarball requirement.
+# This assumes you build the package from inside the main project repository.
+source=()
+sha256sums=()
+
+# Local source directory name under $srcdir
+_srcdir_name="source"
+
+prepare() {
+  mkdir -p "$srcdir/$_srcdir_name"
+  rsync -a \
+    --exclude=".git" \
+    --exclude=".github" \
+    --exclude="pkg" \
+    --exclude="srcpkg" \
+    "$startdir/" "$srcdir/$_srcdir_name/"
+}
+
+build() {
+  cd "$srcdir/$_srcdir_name"
+  :
+}
+
+package() {
+  cd "$srcdir/$_srcdir_name"
+
+  # Install the wrapper into /usr/bin
+  install -Dm0755 "scripts/pkgmgr-wrapper.sh" \
+    "$pkgdir/usr/bin/pkgmgr"
+
+  # Install Nix init helper
+  install -Dm0755 "scripts/init-nix.sh" \
+    "$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"
+}