Refine setup workflows and add architecture map

- Split virgin tests into separate root and user GitHub Actions workflows
  (test-virgin-root, test-virgin-user) and adjust Arch container flows
- Introduce scripts/installation/venv-create.sh and reuse it from
  scripts/installation/main.sh with separate root/system and user/dev paths
- Add PKGMGR architecture & setup map (assets/map.png) and section in README
  with link to the up-to-date master page
- Simplify README by removing outdated Docker quickstart, usage examples,
  and AI footer
- Extend .gitignore to exclude src/source artifacts

https://chatgpt.com/share/6939bbfe-5cb0-800f-8ea8-95628dc911f5

.gitignore

@@ -15,7 +15,7 @@ dist/
 build/*
 *.egg-info/
 pkg
-
+src/source
 package-manager-*
 
 # debian