Code Reviews generate "unexpected error when processing the request"

## Problem
Similar to #7683 - Getting `Encountered an unexpected error when processing the request, please try again` when trying to perform a code review.

## Steps to reproduce the issue

1. From chat, attempt to run a code review.
2. Select the option to run a review only on the requested file
3. Receive an error.

## Expected behavior
Code reviews should not generate a unexpected error.

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

- OS: Darwin arm64 25.0.0
- Visual Studio Code extension host: 1.102.1
- Amazon Q: 1.83.0
- node: 22.15.1
- electron: 35.6.0

Start by reproducing the code-review flow in the VS Code extension: from chat, request a review and select only the requested file. Compare the failure with issue #7683 and trace the resulting error; done means that this flow completes without the unexpected-error message.

Written by the indexing model from the issue text.