fix(test): resolve data race in TTS concurrent test mock

Add stateless flag to mockTTSProvider to skip capturing opts
during concurrent tests. Prevents race on capturedOpts field.

internal/http/tts_test.go

@@ -25,12 +25,15 @@ type mockTTSProvider struct {
 	result       *audio.SynthResult
 	err          error
 	block        bool // if true, blocks until ctx is cancelled (timeout test)
+	stateless    bool // if true, don't capture opts (for concurrent tests)
 }
 
 func (m *mockTTSProvider) Name() string { return m.name }
 
 func (m *mockTTSProvider) Synthesize(ctx context.Context, text string, opts audio.TTSOptions) (*audio.SynthResult, error) {
-	m.capturedOpts = opts
+	if !m.stateless {
+		m.capturedOpts = opts
+	}
 	if m.block {
 		<-ctx.Done()
 		return nil, ctx.Err()

internal/http/tts_update_manager_test.go

@@ -66,9 +66,9 @@ func TestTTSHandler_UpdateManager_SwapsProvider(t *testing.T) {
 func TestTTSHandler_UpdateManager_ConcurrentSafe(t *testing.T) {
 	setupTestToken(t, "") // dev mode
 
-	// Use stateless mock — each provider is separate instance
+	// Use stateless mock to avoid race on capturedOpts
 	mgr := audio.NewManager(audio.ManagerConfig{Primary: "mock"})
-	mgr.RegisterTTS(&mockTTSProvider{name: "mock"})
+	mgr.RegisterTTS(&mockTTSProvider{name: "mock", stateless: true})
 
 	h := NewTTSHandler(mgr)
 	mux := http.NewServeMux()
@@ -96,7 +96,7 @@ func TestTTSHandler_UpdateManager_ConcurrentSafe(t *testing.T) {
 	go func() {
 		defer wg.Done()
 		newMgr := audio.NewManager(audio.ManagerConfig{Primary: "mock-new"})
-		newMgr.RegisterTTS(&mockTTSProvider{name: "mock-new"})
+		newMgr.RegisterTTS(&mockTTSProvider{name: "mock-new", stateless: true})
 		h.UpdateManager(newMgr)
 	}()