Add minimal developer README

README.md

@@ -1,3 +1,23 @@
 # Documentation
 
-This repository will host organisation-wide documentation (e.g., MkDocs or Docusaurus).
+## Overview
+Central documentation for the organisation: architecture, ADRs, runbooks, and user guides.
+
+## Scope
+- Developer and operator documentation
+- Architecture Decision Records (ADRs)
+- Public and internal guides
+
+## Tooling
+TBD (e.g., Docusaurus or MkDocs)
+
+## Structure
+- `docs/` site content (to be added)
+- `docs/adr/` architecture decisions
+- `static/` assets (if used by the site)
+
+## Local build
+Depends on chosen site generator. Add commands once the tool is selected.
+
+## Contributions
+Keep documentation in British English. Align updates with code changes.