v0.4.0

What's New

• Contact sync — Agent syncs server contacts to local TrustStore on startup (additive, non-fatal)
• Bidirectional contact push — AddContact() / RemoveContact() propagate changes to server (best-effort)
• Agent-to-agent contact requests — SendContactRequest() via server REST API with P2P Envelope fallback; whitelist bypass for incoming requests
• Signaling error handling — Agent processes signaling_error messages from server (e.g., "not in contacts" rejection), fails pending connections with clear error
• RegistryClient auth — Ed25519 signature authentication for contacts and contact-request endpoints

Cleanup

• Removed unused NostrSignaling + CompositeSignaling (875 lines) — tracked in CANDIDATE_FEATURES.md
• Removed unused DomainVerifier + RecoveryManager (148 lines) — tracked in CANDIDATE_FEATURES.md
• Removed DHT reference from Discovery interface comment

Dependencies

• Bumped peerclaw-core to v0.6.0