Construct Doesn't Load Without Developer Web-Server Running

I had a developer test add-on running at http://localhost:8080; Everything worked as expected. However, after uninstalling the add-on, Construct no longer loads unless that web-server is running. If clear the browser cache it'll run.

Am I forever beholden to running that web-server just to open Construct - even if I'm not using that plugin?

One thing you can check is, open the dev tools (f12), there should be an application tab, you should see IndexDB if you expand it, there should be an item called localforage - https://editor.construct.net, if you select it your going to see a list of key-value pairs there should be one called c3-dev-addon-list, make sure your dev addon is not there, you can also remove that property manually (but it will remove all your dev addons)

Just remove your test addon from the Addon Manager.