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

- Replace msgpack encoding with protobuf wire format
- Update field names to proto convention (SessionId)
- Cast int fields to int32 (ChunkIndex, TotalChunks, SampleRate, Count)
- Use pointer slices for repeated messages ([]*TTSVoiceInfo)
- Rewrite tests for proto round-trips

e2e_test.go

@@ -12,7 +12,7 @@ import (
 	"testing"
 
 	"git.daviestechlabs.io/daviestechlabs/handler-base/messages"
-	"github.com/vmihailenco/msgpack/v5"
+	"google.golang.org/protobuf/proto"
 )
 
 // ────────────────────────────────────────────────────────────────────────────
@@ -67,21 +67,21 @@ func TestSynthesisE2E_StreamChunks(t *testing.T) {
 
 		// Verify typed chunk struct
 		msg := messages.TTSAudioChunk{
-			SessionID:   "test-session",
-			ChunkIndex:  chunkIdx,
-			TotalChunks: totalChunks,
+			SessionId:   "test-session",
+			ChunkIndex:  int32(chunkIdx),
+			TotalChunks: int32(totalChunks),
 			Audio:       chunk,
 			IsLast:      isLast,
 			SampleRate:  24000,
 		}
 
 		// Round-trip through msgpack
-		data, _ := msgpack.Marshal(&msg)
+		data, _ := proto.Marshal(&msg)
 		var decoded messages.TTSAudioChunk
-		_ = msgpack.Unmarshal(data, &decoded)
+		_ = proto.Unmarshal(data, &decoded)
 
-		if decoded.SessionID != "test-session" {
-			t.Errorf("chunk %d: session = %v", chunkIdx, decoded.SessionID)
+		if decoded.SessionId != "test-session" {
+			t.Errorf("chunk %d: session = %v", chunkIdx, decoded.SessionId)
 		}
 		if decoded.IsLast != isLast {
 			t.Errorf("chunk %d: is_last = %v, want %v", chunkIdx, decoded.IsLast, isLast)
@@ -266,13 +266,13 @@ func BenchmarkAudioChunking(b *testing.B) {
 			}
 			chunk := audioBytes[i:end]
 			msg := &messages.TTSAudioChunk{
-				SessionID:   "bench",
-				ChunkIndex:  i / chunkSize,
-				TotalChunks: totalChunks,
+				SessionId:   "bench",
+				ChunkIndex:  int32(i / chunkSize),
+				TotalChunks: int32(totalChunks),
 				Audio:       chunk,
 				SampleRate:  24000,
 			}
-			_, _ = msgpack.Marshal(msg)
+			_, _ = proto.Marshal(msg)
 		}
 	}
 }