feat(gomsg): pymsg/libmsg 协议的 Go 实现，waf logclient 抽取接入

- 新增 gomsg/：帧协议（4B 大端长度 + UTF-8，64MiB 上限）、MsgClient/MsgServer、
  RpcClient/RpcServer（_route 分发、错误脱敏、panic 恢复、json.Number 保精度）、
  AsyncQueue[T]、LogClient（集中式日志，级别过滤 + fail-safe），线协议与 Python/C++ 字节级兼容
- waf/internal/logclient 改为 gomsg 薄适配层（336→20 行），main/engine/proxy 零改动
- gomsg 26 项单测全绿（-race）；waf 编译通过

gomsg/frame_test.go

@@ -0,0 +1,66 @@
+package gomsg
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"testing"
+)
+
+func TestEncodeRoundTrip(t *testing.T) {
+	payload := []byte(`{"hello":"世界"}`)
+	frame, err := Encode(payload)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(frame) != 4+len(payload) {
+		t.Fatalf("frame length = %d, want %d", len(frame), 4+len(payload))
+	}
+	if got := binary.BigEndian.Uint32(frame[:4]); got != uint32(len(payload)) {
+		t.Fatalf("header = %d, want %d", got, len(payload))
+	}
+	got, err := ReadFrame(bytes.NewReader(frame), 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(got, payload) {
+		t.Fatalf("payload mismatch: %q", got)
+	}
+}
+
+func TestEncodeTooLarge(t *testing.T) {
+	payload := make([]byte, MaxMsgSize+1)
+	if _, err := Encode(payload); err == nil {
+		t.Fatal("expected error for oversized payload")
+	}
+}
+
+func TestReadFrameTooLarge(t *testing.T) {
+	header := make([]byte, 4)
+	binary.BigEndian.PutUint32(header, MaxMsgSize+1)
+	_, err := ReadFrame(bytes.NewReader(header), 0)
+	if err == nil {
+		t.Fatal("expected error for oversized header")
+	}
+}
+
+func TestReadFrameTruncated(t *testing.T) {
+	frame, _ := Encode([]byte("abcdef"))
+	if _, err := ReadFrame(bytes.NewReader(frame[:len(frame)-3]), 0); err == nil {
+		t.Fatal("expected error for truncated payload")
+	}
+}
+
+func TestReadFrameMaxParam(t *testing.T) {
+	frame, _ := Encode([]byte("hello"))
+	if _, err := ReadFrame(bytes.NewReader(frame), 4); err == nil {
+		t.Fatal("expected error when max < payload length")
+	}
+}
+
+func TestReadFrameEOF(t *testing.T) {
+	if _, err := ReadFrame(bytes.NewReader(nil), 0); !errors.Is(err, io.EOF) {
+		t.Fatalf("expected EOF, got %v", err)
+	}
+}