feat(p2p): add missing response encoders for P2P listener

HandshakeResponse.Encode, HandshakeRequest.Decode,
RequestChain.Decode, ResponseChainEntry.Encode — all using
go-p2p's EncodeStorage/DecodeStorage.

These enable the Go node to accept incoming P2P connections
and serve blocks to other peers (full seed node capability).

Co-Authored-By: Charon <charon@lethean.io>

p2p/encode.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2017-2026 Lethean (https://lt.hn)
+//
+// Licensed under the European Union Public Licence (EUPL) version 1.2.
+// SPDX-License-Identifier: EUPL-1.2
+
+package p2p
+
+import (
+	levin "dappco.re/go/core/p2p/node/levin"
+)
+
+// Encode serialises a HandshakeResponse to a portable storage blob.
+//
+//	data, err := resp.Encode()
+func (r *HandshakeResponse) Encode() ([]byte, error) {
+	s := levin.Section{
+		"node_data":    levin.ObjectVal(r.NodeData.MarshalSection()),
+		"payload_data": levin.ObjectVal(r.PayloadData.MarshalSection()),
+	}
+	if len(r.PeerlistBlob) > 0 {
+		s["local_peerlist"] = levin.StringVal(r.PeerlistBlob)
+	}
+	return levin.EncodeStorage(s)
+}
+
+// Decode parses a RequestChain from a portable storage blob.
+//
+//	err := req.Decode(data)
+func (r *RequestChain) Decode(data []byte) error {
+	s, err := levin.DecodeStorage(data)
+	if err != nil {
+		return err
+	}
+	if v, ok := s["block_ids"]; ok {
+		arr, err := v.AsStringArray()
+		if err != nil {
+			return err
+		}
+		r.BlockIDs = make([][]byte, len(arr))
+		for i, b := range arr {
+			r.BlockIDs[i] = b
+		}
+	}
+	return nil
+}
+
+// Encode serialises a ResponseChainEntry to a portable storage blob.
+//
+//	data, err := resp.Encode()
+func (r *ResponseChainEntry) Encode() ([]byte, error) {
+	blockIDs := make([][]byte, len(r.BlockIDs))
+	for i, id := range r.BlockIDs {
+		blockIDs[i] = id
+	}
+	s := levin.Section{
+		"start_height": levin.Uint64Val(r.StartHeight),
+		"total_height": levin.Uint64Val(r.TotalHeight),
+		"m_block_ids":  levin.StringArrayVal(blockIDs),
+	}
+	return levin.EncodeStorage(s)
+}
+
+// Decode parses a HandshakeRequest from a portable storage blob.
+//
+//	err := req.Decode(data)
+func (r *HandshakeRequest) Decode(data []byte) error {
+	s, err := levin.DecodeStorage(data)
+	if err != nil {
+		return err
+	}
+	if v, ok := s["node_data"]; ok {
+		obj, err := v.AsSection()
+		if err != nil {
+			return err
+		}
+		if err := r.NodeData.UnmarshalSection(obj); err != nil {
+			return err
+		}
+	}
+	if v, ok := s["payload_data"]; ok {
+		obj, err := v.AsSection()
+		if err != nil {
+			return err
+		}
+		if err := r.PayloadData.UnmarshalSection(obj); err != nil {
+			return err
+		}
+	}
+	return nil
+}