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

scripts/installation/ubuntu/package.sh

@@ -3,6 +3,25 @@ set -euo pipefail
 
 echo "[ubuntu/package] Building Ubuntu (Debian-style) package..."
 
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "${SCRIPT_DIR}/../.." && pwd)"
+
+BUILD_ROOT="/tmp/package-manager-ubuntu-build"
+rm -rf "${BUILD_ROOT}"
+mkdir -p "${BUILD_ROOT}"
+
+echo "[ubuntu/package] Syncing project sources to ${BUILD_ROOT}..."
+rsync -a \
+  --exclude 'packaging/debian' \
+  "${PROJECT_ROOT}/" "${BUILD_ROOT}/"
+
+echo "[ubuntu/package] Overlaying debian/ metadata from packaging/debian..."
+mkdir -p "${BUILD_ROOT}/debian"
+cp -a "${PROJECT_ROOT}/packaging/debian/." "${BUILD_ROOT}/debian/"
+
+cd "${BUILD_ROOT}"
+
+echo "[ubuntu/package] Running dpkg-buildpackage..."
 dpkg-buildpackage -us -uc -b
 
 echo "[ubuntu/package] Installing generated DEB package..."