Follow-up from owasp-docker removal / maturity: removed refactor.

Add a new subsection under ## Removed Artifacts in docs/architecture/ai-artifacts.md documenting how to reactivate a previously-removed artifact:

1. Delete the maturity: removed line from the artifact's entry in the relevant collections/*.collection.yml file.
2. If the underlying file was deleted, restore it (e.g., git checkout -- ).
3. Run
   pm run plugin:generate to regenerate plugin outputs and the hve-core-all collection.
4. Verify the artifact reappears in the relevant plugin manifests and in collections/hve-core-all.collection.yml.
5. Run
   pm run lint:all and
   pm run test:ps to confirm the reactivation is clean.

Keep the section adjacent to the existing Collection-YAML Marker subsection.