Thanks again jan2000 ! I reworded my original question to be a little more to the point and less alarmist
There just weren't any instructions included on how to export the project and make it work once it was out of Construct 2's preview mode, so I assumed that wasn't how the plugin was designed.
I'd love to see an amended tutorial that covers exporting, since XAMPP seems a bit complicated for people like myself without networking experience. For example, do I need the XAMPP server and the breakout server running?
Also, I was successfully using my phone on the network to control the Arduino plugged into my PC, but will I lose that functionality without the C2 preview server running (in which case, I might make my final "app" use the Multiplayer plugin and signalling server as well, which could even grant remote access).
In a dream world I'd also love to know how you got the Arduino working over wifi with the ESP8266 But I know your time is valuable and that's beyond the scope of this plugin... so maybe if there were another plugin for Arduino Wifi I'd buy that, too (once I figure out how to get the Arduino plugin working in an exported project, anyway)!