Fix P2P message forwarding for Custom challenge messages

Previously, ChallengeMessageType::Custom messages (used by p2p_bridge for
proposal voting) were not forwarded to challenge containers because they
fell through to the catch-all branch returning None.

This caused proposal timeouts because validators never received votes
from other validators - the P2P messages were broadcast but never
delivered to the term-challenge containers.

Now Custom messages are properly parsed as ChallengeP2PMessage and
forwarded to the container's /p2p/message endpoint.

Author: echobt

bins/validator-node/src/main.rs

@@ -3230,6 +3230,22 @@ async fn handle_message(
                             None
                         }
                     }
+                    platform_core::ChallengeMessageType::Custom(ref custom_type) => {
+                        // For p2p_bridge messages, forward the raw payload as ChallengeP2PMessage
+                        if let Ok(p2p_msg) = serde_json::from_slice::<
+                            platform_challenge_sdk::ChallengeP2PMessage,
+                        >(&msg_payload)
+                        {
+                            debug!(
+                                "Forwarding Custom({}) message to challenge container",
+                                custom_type
+                            );
+                            Some(p2p_msg)
+                        } else {
+                            warn!("Failed to parse Custom({}) payload as ChallengeP2PMessage", custom_type);
+                            None
+                        }
+                    }
                     _ => {
                         debug!(
                             "Unhandled challenge message type: {:?}",