fix(lint): remove unused imports in encryption modules

Fixes F401 lint errors in agent-mesh:
- x3dh.py: remove unused os, VerifyKey imports
- channel.py: remove unused X3DHResult import
- bridge.py: remove unused field, Optional imports

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: imran-siddique

packages/agent-mesh/src/agentmesh/encryption/bridge.py

@@ -20,8 +20,7 @@
 from __future__ import annotations
 
 import logging
-from dataclasses import dataclass, field
-from typing import Optional
+from dataclasses import dataclass
 
 from agentmesh.encryption.channel import ChannelEstablishment, SecureChannel
 from agentmesh.encryption.x3dh import InMemoryPreKeyStore, PreKeyBundle, PreKeyStore, X3DHKeyManager

packages/agent-mesh/src/agentmesh/encryption/channel.py

@@ -19,7 +19,7 @@
 from dataclasses import dataclass
 
 from agentmesh.encryption.ratchet import DoubleRatchet, EncryptedMessage
-from agentmesh.encryption.x3dh import PreKeyBundle, X3DHKeyManager, X3DHResult
+from agentmesh.encryption.x3dh import PreKeyBundle, X3DHKeyManager
 
 logger = logging.getLogger(__name__)
 

packages/agent-mesh/src/agentmesh/encryption/x3dh.py

@@ -12,7 +12,6 @@
 from __future__ import annotations
 
 import logging
-import os
 import secrets
 from dataclasses import dataclass, field
 from typing import Protocol
@@ -324,8 +323,6 @@ def respond(
     @staticmethod
     def _verify_signed_pre_key(bundle: PreKeyBundle) -> None:
         """Verify the signed pre-key signature against the identity key."""
-        from nacl.signing import VerifyKey
-
         # Convert X25519 identity key back to Ed25519 is not directly possible,
         # so we verify using the signature which was created with Ed25519.
         # The bundle must carry enough info to verify. For now, we verify