fix: delete orphaned onion service on concurrent start race

If two goroutines raced through Start(), the losing goroutine would
close the control connection but leave an orphaned hidden service
on the Tor daemon. Now we call DelOnion before closing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: AOrobator

tor/tor.go

@@ -155,7 +155,8 @@ func (s *Service) Start(cfg *Config) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	if s.running {
-		// Another goroutine started concurrently — clean up
+		// Another goroutine started concurrently — clean up orphaned onion service
+		_ = ctrl.DelOnion(resp.ServiceID)
 		ctrl.Close()
 		return errors.New("tor service was started concurrently")
 	}