Bring wire protocol into full YAW/2 spec compliance

Five interop issues fixed against PROTOCOL.md:

- Join signature now covers nonce_raw || net_ascii (64-char UTF-8 hex
  string) as specified in §5.1, not net_raw_bytes. Both anchor server
  and client updated to match.

- Chat wire fields renamed to spec names: text/ts (Unix ms int64)
  replacing body/sent_at (ISO timestamp). Flat layout on PeerMessage
  matches §8 exactly; store and TUI updated accordingly.

- Direct messages now use the spec "pm" type (flat {type,mid,text,ts})
  instead of chat+to. Receiver reconstructs a ChatMessage with
  dm:<short-id> room for IPC/storage. §8 compliant.

- File transfer message types changed to spec hyphenated names:
  file-offer, file-accept, file-cancel, file-done with spec field
  names (name/size not filename/size_bytes). §9 compliant.

- DataChannel open-race (§14 gotcha #3) fixed with sync.Once: doOpen
  fires on OnOpen callback or immediately if the channel is already
  open when WireDataChannel is called (answerer race).

Also fixes two bugs found during testing:

- mid was missing from outgoing wire messages, causing all received
  messages to arrive with mid="" and collide on the UNIQUE DB
  constraint. mid is now included on all sent chat/pm messages; a
  random mid is generated for any received message that omits it.

- Test scripts hardened: kill -9 + active lsof polling replaces blind
  sleep for port cleanup; join_network sent before peer_field queries
  (local_peer is now network-scoped and nil until joined).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/mesh/peer.go

@@ -2,10 +2,13 @@
 package mesh
 
 import (
+	"crypto/rand"
 	"encoding/hex"
 	"encoding/json"
 	"log"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/pion/webrtc/v3"
 
@@ -21,7 +24,7 @@ type Anchor interface {
 }
 
 // WireDataChannel sets up open/message/close handlers on a "yaw" DataChannel.
-// Must be called before the DataChannel opens.
+// Safe to call whether the channel is already open or not (§6 open-race).
 func WireDataChannel(
 	dc *webrtc.DataChannel,
 	pc *webrtc.PeerConnection,
@@ -31,7 +34,8 @@ func WireDataChannel(
 ) {
 	sendCh := make(chan []byte, 64)
 
-	dc.OnOpen(func() {
+	var once sync.Once
+	doOpen := func() {
 		log.Printf("peer: DataChannel open with %s", peerID.Short())
 
 		// Send hello — bind our identity to this DTLS session.
@@ -69,7 +73,13 @@ func WireDataChannel(
 				}
 			}
 		}()
-	})
+	}
+
+	dc.OnOpen(func() { once.Do(doOpen) })
+	// §6 gotcha: answerer's DC may already be open when OnDataChannel fires.
+	if dc.ReadyState() == webrtc.DataChannelStateOpen {
+		once.Do(doOpen)
+	}
 
 	dc.OnMessage(func(msg webrtc.DataChannelMessage) {
 		if msg.IsString {
@@ -152,8 +162,30 @@ func handleDCMessage(data []byte, from proto.PeerID, localID *crypto.Identity, m
 
 func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 	switch msg.Type {
+	case proto.MsgChat:
+		chat := &proto.ChatMessage{
+			Mid:  midOrRandom(msg.Mid),
+			From: from,
+			Room: msg.Room,
+			Text: msg.Text,
+			Ts:   msg.Ts,
+		}
+		m.SaveMessage(chat)
+		m.Emit(proto.IpcMessage{Type: proto.EvtMessageReceived, Message: chat})
+
+	case proto.MsgPm:
+		// Private message — reconstruct as ChatMessage for IPC/storage using dm:<short-id> room.
+		chat := &proto.ChatMessage{
+			Mid:  midOrRandom(msg.Mid),
+			From: from,
+			Room: "dm:" + from.Short(),
+			Text: msg.Text,
+			Ts:   msg.Ts,
+		}
+		m.SaveMessage(chat)
+		m.Emit(proto.IpcMessage{Type: proto.EvtMessageReceived, Message: chat})
+
 	case proto.MsgFileListReq:
-		// Peer wants our file list — reply directly on their send channel.
 		files := m.ScanShareDir()
 		resp, err := json.Marshal(proto.PeerMessage{
 			Type:         proto.MsgFileListResp,
@@ -165,7 +197,6 @@ func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 		m.SendTo(from, resp)
 
 	case proto.MsgFileListResp:
-		// Received a remote peer's file list — forward to IPC subscribers.
 		if msg.FileListResp != nil {
 			m.Emit(proto.IpcMessage{
 				Type:   proto.EvtFileList,
@@ -174,11 +205,13 @@ func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 			})
 		}
 
-	case proto.MsgChat:
-		if msg.Chat != nil {
-			m.SaveMessage(msg.Chat)
-			m.Emit(proto.IpcMessage{Type: proto.EvtMessageReceived, Message: msg.Chat})
-		}
+	case proto.MsgFileOffer:
+		m.Emit(proto.IpcMessage{
+			Type:   proto.EvtIncomingFile,
+			PeerID: peerIDPtr(from),
+			Offer:  &proto.FileOffer{Xid: msg.Xid, Name: msg.Name, Size: msg.Size, SHA256: msg.SHA256},
+		})
+
 	case proto.MsgPeerGossip:
 		if msg.Gossip != nil {
 			log.Printf("mesh: gossip from %s: %d peer hints", from.Short(), len(msg.Gossip.Peers))
@@ -187,19 +220,24 @@ func dispatchPeerMessage(msg proto.PeerMessage, from proto.PeerID, m *Mesh) {
 		log.Printf("mesh: ping from %s", from.Short())
 	case proto.MsgPong:
 		log.Printf("mesh: pong from %s", from.Short())
-	case proto.MsgFileOffer:
-		if msg.FileOffer != nil {
-			m.Emit(proto.IpcMessage{
-				Type:   proto.EvtIncomingFile,
-				PeerID: peerIDPtr(from),
-				Offer:  msg.FileOffer,
-			})
-		}
 	default:
 		log.Printf("mesh: unknown message type %q from %s", msg.Type, from.Short())
 	}
 }
 
+// midOrRandom returns mid if non-empty, otherwise generates a random 16-byte hex string.
+// Ensures every stored message has a unique mid even from peers that don't send one.
+func midOrRandom(mid string) string {
+	if mid != "" {
+		return mid
+	}
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		return hex.EncodeToString([]byte(time.Now().String()))
+	}
+	return hex.EncodeToString(b)
+}
+
 func dtlsFingerprints(pc *webrtc.PeerConnection) (local, remote []byte) {
 	if ld := pc.LocalDescription(); ld != nil {
 		local = fingerprintFromSDP(ld.SDP)