Unable to set python interpreter when workspace not trusted, but also no trust popup

I teach in a data science program, and over the past two weeks have had to work with ~60 students on environment management, and I have to say it's been more painful this year than ever before.

One major issue I kept finding is students would try to change their default interpreter (or active interpreter) to a working miniforge3 installation, and the change just wouldn't stick. No error messages, no popups, nothing. The change would appear in the user settings JSON, but Python wouldn't respect it and would just stick to using the os-bundled version of Python.

I did eventually figure out I could get around this by:

- In VS Code, use `open folder` to open the student's user directory.
- This would cause a "trust this workspace?" bar to pop up.
- If I clicked manage and trust, *then* I would regain the ability to select interpreters.

This happened on mac and windows, and all with new installs done during the past two week or so.

If this is a desired behavior (I don't really get what "trusted workspace" is trying to protect), then it shouldn't be a silent failure — there should be an informative popup with instructions on correcting the problem.

If it isn't desired, it should definitely be fixed — it's really hurting the onboarding process for new users.

No file or test is named. Reproduce interpreter selection in an untrusted workspace on macOS or Windows, then compare the behavior before and after trusting the workspace. Done means the interpreter change works as intended or the user receives an informative explanation and recovery instructions instead of a silent failure.

Written by the indexing model from the issue text.