Twelve-page Markdown doc set covering installation, configuration (full
env-var reference), deployment/HTTPS, authentication/OIDC, the user guide,
workspaces, networking, administration, security model, API reference, and
troubleshooting. Link it from the README nav and point SETUP.md at it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>