feat: migrate from msgpack to protobuf (handler-base v1.0.0)

- Replace msgpack encoding with protobuf wire format
- Update field names to proto convention
- Use pointer slices for repeated message fields ([]*DocumentSource)
- Rewrite tests for proto round-trips

main_test.go

@@ -5,26 +5,26 @@ import (
 
 	"git.daviestechlabs.io/daviestechlabs/handler-base/messages"
 	"git.daviestechlabs.io/daviestechlabs/handler-base/natsutil"
-	"github.com/vmihailenco/msgpack/v5"
+	"google.golang.org/protobuf/proto"
 )
 
 func TestVoiceRequestDecode(t *testing.T) {
-	req := messages.VoiceRequest{
-		RequestID:  "req-123",
+	req := &messages.VoiceRequest{
+		RequestId:  "req-123",
 		Audio:      []byte{0x01, 0x02, 0x03},
 		Language:   "en",
 		Collection: "docs",
 	}
-	data, err := msgpack.Marshal(&req)
+	data, err := proto.Marshal(req)
 	if err != nil {
 		t.Fatal(err)
 	}
-	decoded, err := natsutil.Decode[messages.VoiceRequest](data)
-	if err != nil {
+	var decoded messages.VoiceRequest
+	if err := natsutil.Decode(data, &decoded); err != nil {
 		t.Fatal(err)
 	}
-	if decoded.RequestID != "req-123" {
-		t.Errorf("RequestID = %q", decoded.RequestID)
+	if decoded.RequestId != "req-123" {
+		t.Errorf("RequestId = %q", decoded.RequestId)
 	}
 	if len(decoded.Audio) != 3 {
 		t.Errorf("Audio len = %d", len(decoded.Audio))
@@ -32,19 +32,19 @@ func TestVoiceRequestDecode(t *testing.T) {
 }
 
 func TestVoiceResponseRoundtrip(t *testing.T) {
-	resp := messages.VoiceResponse{
-		RequestID:     "req-456",
+	resp := &messages.VoiceResponse{
+		RequestId:     "req-456",
 		Response:      "It is sunny today.",
 		Audio:         make([]byte, 8000),
 		Transcription: "What is the weather?",
-		Sources:       []messages.DocumentSource{{Text: "weather doc", Score: 0.9}},
+		Sources:       []*messages.DocumentSource{{Text: "weather doc", Score: 0.9}},
 	}
-	data, err := msgpack.Marshal(&resp)
+	data, err := proto.Marshal(resp)
 	if err != nil {
 		t.Fatal(err)
 	}
 	var got messages.VoiceResponse
-	if err := msgpack.Unmarshal(data, &got); err != nil {
+	if err := proto.Unmarshal(data, &got); err != nil {
 		t.Fatal(err)
 	}
 	if got.Response != "It is sunny today." {