Landscape guidance

Follow adr/README.md and specs/README.md for document lifecycle rules.
Each specification identifies affected repositories; maintain systems.md when responsibilities or ownership boundaries change.
Implementation, runtime configuration and validation evidence belong to their application repositories. Reusable engineering resources belong to engineering.
Engineering skills are available in the engineering repository under resources/skills, or in a consuming project's pinned generated/skills.
Do not infer permission for production deployment from documentation changes.