fix: avoid duplicate error messages in WebSocket copy handlers

When the copy handler sends a result or error message to the client,
don't also return an error which causes the caller to send another
error message.

Author: rgarcia

cmd/api/api/cp.go

@@ -267,10 +267,8 @@ func (s *ApiService) handleCopyTo(ctx context.Context, ws *websocket.Conn, inst
 	resultJSON, _ := json.Marshal(result)
 	ws.WriteMessage(websocket.TextMessage, resultJSON)
 
-	if !resp.Success {
-		return fmt.Errorf("guest copy failed: %s", resp.Error)
-	}
-
+	// Don't return an error here - the result message already contains any error info.
+	// Returning an error would cause the caller to send a duplicate error message.
 	return nil
 }
 
@@ -348,7 +346,9 @@ func (s *ApiService) handleCopyFrom(ctx context.Context, ws *websocket.Conn, ins
 			}
 			errJSON, _ := json.Marshal(cpErr)
 			ws.WriteMessage(websocket.TextMessage, errJSON)
-			return fmt.Errorf("guest error at %s: %s", r.Error.Path, r.Error.Message)
+			// Don't return an error here - the error message was already sent to the client.
+			// Returning an error would cause the caller to send a duplicate error message.
+			return nil
 		}
 	}