Live E2E found that replaying a pre-logout cookie still authenticated (200, not
401): SignOutAsync only clears the CLIENT cookie, but the stateless encrypted
cookie ticket stays valid server-side because its security stamp is unchanged —
a captured cookie was replayable after logout until ticket expiry.
Fix: logout now rotates the local-admin security stamp (RotateLocalAdminSecurityStamp),
so every outstanding local session (old stamp) fails OnValidatePrincipal on its
next request. For the single admin this is "log out everywhere". Gated on an
authenticated local session so an unauthenticated caller can't force-revoke the
admin. OIDC sessions (no stamp) are unaffected; SignOutAsync still clears the
client cookie for UX.
+2 handler tests (rotate-when-configured / no-op-when-unconfigured). Auth suite
green (21). Docs: decisions.md note updated.
Refs #295
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
