membership/auth_test: golden (signed+registered accepted), error paths
(unregistered 401, replayed nonce 401, clock skew 401, tampered body 401,
missing headers 401), exemptions (healthz, soft allows, off no-op).
client_test: end-to-end with the real client against an enforce server —
registered peer accepted, unregistered rejected, revoked peer denied without
a server restart.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
