ADR-023: Authentication Target Architecture
Target authentication architecture for SecurityV0 — portal UI, API, and infrastructure access. Three IdPs (GitHub at L1 perimeter, WorkOS at L2 application, Entra at L3 Azure RBAC), four SSH tiers including a narrow Tier-1.5 emergency key, an Active subscription-Owner Entra account (no PIM, no backup SP — 2nd-human-Owner is the rollback) with Security Defaults MFA-on-sign-in.