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/ipc/ipc.go

@@ -16,7 +16,6 @@ import (
 	"net"
 	"time"
 
-	"github.com/google/uuid"
 	"github.com/waste-go/internal/invite"
 	"github.com/waste-go/internal/netmgr"
 	"github.com/waste-go/internal/proto"
@@ -49,9 +48,11 @@ func handleClient(conn net.Conn, mgr *netmgr.Manager) {
 
 	writeCh := make(chan []byte, 128)
 	done := make(chan struct{})
+	writerDone := make(chan struct{})
 
 	// Writer goroutine.
 	go func() {
+		defer close(writerDone)
 		w := bufio.NewWriter(conn)
 		for line := range writeCh {
 			line = append(line, '\n')
@@ -140,30 +141,63 @@ func handleClient(conn net.Conn, mgr *netmgr.Manager) {
 				send(errMsg("send_message: not joined to any network"))
 				continue
 			}
-			msg := &proto.ChatMessage{
-				Mid:    randomHex(16),
-				ID:     uuid.NewString(),
-				From:   n.Identity.PeerID(),
-				To:     cmd.To,
-				Room:   cmd.Room,
-				Body:   cmd.Body,
-				SentAt: time.Now(),
-			}
-			payload, err := json.Marshal(proto.PeerMessage{Type: proto.MsgChat, Chat: msg})
-			if err != nil {
-				continue
-			}
+			ts := time.Now().UnixMilli()
 			if cmd.To != nil {
-				n.Mesh.SendTo(*cmd.To, payload)
+				// DM → spec "pm" type: flat {type, mid, text, ts} on the wire
+				mid := randomHex(16)
+				wire, err := json.Marshal(proto.PeerMessage{
+					Type: proto.MsgPm,
+					Mid:  mid,
+					Text: cmd.Body,
+					Ts:   ts,
+				})
+				if err != nil {
+					continue
+				}
+				n.Mesh.SendTo(*cmd.To, wire)
+				// Store locally with dm:<short-id> room convention
+				local := &proto.ChatMessage{
+					Mid:  mid,
+					From: n.Identity.PeerID(),
+					To:   cmd.To,
+					Room: "dm:" + (*cmd.To).Short(),
+					Text: cmd.Body,
+					Ts:   ts,
+				}
+				n.Mesh.SaveMessage(local)
+				n.Mesh.Emit(proto.IpcMessage{
+					Type:      proto.EvtMessageReceived,
+					NetworkID: n.ID,
+					Message:   local,
+				})
 			} else {
-				n.Mesh.Broadcast(payload)
+				// Group chat → spec "chat" type: flat {type, mid, room, text, ts}
+				mid := randomHex(16)
+				wire, err := json.Marshal(proto.PeerMessage{
+					Type: proto.MsgChat,
+					Mid:  mid,
+					Room: cmd.Room,
+					Text: cmd.Body,
+					Ts:   ts,
+				})
+				if err != nil {
+					continue
+				}
+				n.Mesh.Broadcast(wire)
+				local := &proto.ChatMessage{
+					Mid:  mid,
+					From: n.Identity.PeerID(),
+					Room: cmd.Room,
+					Text: cmd.Body,
+					Ts:   ts,
+				}
+				n.Mesh.SaveMessage(local)
+				n.Mesh.Emit(proto.IpcMessage{
+					Type:      proto.EvtMessageReceived,
+					NetworkID: n.ID,
+					Message:   local,
+				})
 			}
-			n.Mesh.SaveMessage(msg)
-			n.Mesh.Emit(proto.IpcMessage{
-				Type:      proto.EvtMessageReceived,
-				NetworkID: n.ID,
-				Message:   msg,
-			})
 
 		case proto.CmdGetState:
 			send(stateSnapshot(mgr))
@@ -222,6 +256,7 @@ func handleClient(conn net.Conn, mgr *netmgr.Manager) {
 
 	close(done)
 	close(writeCh)
+	<-writerDone // wait for writer to flush before conn.Close() fires
 	log.Printf("ipc: UI client disconnected")
 }