issue #24098: always serve extension clientside code

This is the appropriate way to distinguish which code to serve up in `express.static`. We had been using `debugging: true` to determine if we could serve up extension code, but this ran afoul because even on production machines not all code is built and served through the database. (assets, etc).

The solution here is to allow browser access to the `client` folder of each extension.
Exiting with a non-error is odd here. Unlikely to cause problems though