refactor: companion FrameServer and related (substantive only, no Black)

Reapply refactor from ce8381a (replace monolithic FrameServer with thin
pymc_core subclass, re-export constants, SQLite persistence hooks) while
preserving pre-refactor whitespace where patch applied cleanly. Remaining
files match refactor commit exactly. Diff vs ce8381a is whitespace-only.

Co-authored-by: Cursor <cursoragent@cursor.com>

repeater/handler_helpers/path.py

@@ -13,20 +13,20 @@ class PathHelper:
     async def process_path_packet(self, packet):
 
         from pymc_core.protocol.crypto import CryptoUtils
-        
+
         try:
             if len(packet.payload) < 2:
                 return False
-            
+
             dest_hash = packet.payload[0]
             src_hash = packet.payload[1]
-            
+
             # Get the ACL for this destination identity
             identity_acl = self.acl_dict.get(dest_hash)
             if not identity_acl:
                 logger.debug(f"No ACL for dest 0x{dest_hash:02X}, allowing forward")
                 return False
-            
+
             # Find the client by source hash
             client = None
             for client_info in identity_acl.get_all_clients():
@@ -34,57 +34,59 @@ class PathHelper:
                 if pubkey[0] == src_hash:
                     client = client_info
                     break
-            
+
             if not client:
                 logger.debug(f"PATH packet from unknown client 0x{src_hash:02X}, allowing forward")
                 return False
-            
+
             # Get shared secret for decryption
             shared_secret = client.shared_secret
             if not shared_secret or len(shared_secret) == 0:
                 logger.debug(f"No shared secret for client 0x{src_hash:02X}, cannot decrypt PATH")
                 return False
-            
+
             # Decrypt the PATH packet payload
             # Payload format: dest_hash(1) + src_hash(1) + mac(2) + encrypted_data
             if len(packet.payload) < 4:
                 logger.debug(f"PATH packet too short: {len(packet.payload)} bytes")
                 return False
-            
+
             mac_and_data = packet.payload[2:]  # Skip dest_hash and src_hash
             aes_key = shared_secret[:16]
             decrypted = CryptoUtils.mac_then_decrypt(aes_key, shared_secret, mac_and_data)
-            
+
             if not decrypted:
                 logger.debug(f"Failed to decrypt PATH packet from 0x{src_hash:02X}")
                 return False
-            
+
             # Parse decrypted PATH data
             # Format: path_len(1) + path[path_len] + extra_type(1) + extra[...]
             if len(decrypted) < 1:
                 logger.debug(f"Decrypted PATH data too short")
                 return False
-            
+
             path_len = decrypted[0]
             if len(decrypted) < 1 + path_len:
-                logger.debug(f"PATH data truncated: need {1 + path_len} bytes, got {len(decrypted)}")
+                logger.debug(
+                    f"PATH data truncated: need {1 + path_len} bytes, got {len(decrypted)}"
+                )
                 return False
-            
-            path_data = decrypted[1:1 + path_len]
-            
+
+            path_data = decrypted[1 : 1 + path_len]
+
             # Update client's out_path (same as C++ memcpy)
             client.out_path = bytearray(path_data)
             client.out_path_len = path_len
             client.last_activity = int(time.time())
-            
+
             logger.info(
                 f"Updated out_path for client 0x{src_hash:02X} -> 0x{dest_hash:02X}: "
                 f"path_len={path_len}, path={[hex(b) for b in path_data]}"
             )
-            
+
             # Don't mark as do_not_retransmit - let it forward normally
             return False
-            
+
         except Exception as e:
             logger.error(f"Error processing PATH packet: {e}", exc_info=True)
             return False