Can no longer sign in on non-iam personal account.

## Problem

## Steps to reproduce the issue

## Expected behavior

## System details (run `AWS: About` and/or `Amazon Q: About`)

- OS:
- Visual Studio Code version:
- AWS Toolkit version:
- Amazon Q version:

Start by reproducing the sign-in flow for a personal, non-IAM account in the AWS Toolkit or Amazon Q for Visual Studio Code, using the reported reauthentication and authenticator-code failure. Done means the account can sign in without requiring IAM Identity Center, or the issue has a documented, actionable failure path; the issue provides no file or test names.

Written by the indexing model from the issue text.