Correct the docs I'd written for the (reverted) oauth2-proxy SSO. Reality:
apiserver OIDC rejects all Authentik tokens (design §12), so the dashboard
uses forward-auth (admits kubernetes-* groups) + per-namespace SA token-paste.
Updates authentication.md, multi-tenancy.md, service-catalog, authentik-state,
and add-user skill (onboarding now documents the dashboard token). oauth2-proxy
+ k8s-dashboard OIDC app noted as idle. [ci skip]
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
8e44ccaa65