surface.admin.access permission + seeded Admins system group replaces
hardcoded role == "admin" middleware checks. Admin bypass removed from
RequirePermission — all permissions flow through group membership.
Bootstrap, seed, OIDC, and admin handlers sync group membership on
role changes. Demotion/deletion safeguards use group member count.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
