One crypto path for model-owned *_encrypted columns: assignment encrypts
and RAISES on failure (server.py's accessors print()-ed the error and
silently stored nothing — an agent could 'pair' yet never verify a
signature); read decrypts tolerantly (None + logged warning). is_set()
standardizes the has_secret masking flag. Server adopts it for
api_secret / api_secret_pending; legacy method names kept as delegates.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
