Oh, strike me purple! The problem has gone away. Some unknown combination of keystrokes in my failing attempts to restart everything made the problem disappear. For now. Fingers and toes crossed.
Not sure if this helps, but many years ago we found that using webpack’s eval-source-map option (which at the time was the recommendation for development) requires, as the name suggests, eval-ing code which in turn required us to add unsafe-eval to our manifest.
We asked whether there was any guidance for using a different set of permissions for dev vs production in a single manifest, but alas that was not supported:
We also tracked FRGE-1233 , but as with seemingly most Forge tickets that we’re interested in, this has remained stuck at “Gathering Interest” for over two years…
(Aside for any Atlassian’s looking: From out outsider’s perspective, there’s nothing more infuriating than the “Gathering Interest” status, which is where tickets go to die. If something is gathering interest for multiple years, then you should either decide to do it or mark is as “Won’t fix” so we can all move on with our lives.)