VS Code integrated browser cannot complete Microsoft certificate authentication

### Description

## Steps to reproduce
1. Open an internal Microsoft Power BI report through the browser opened by GitHub Copilot Chat in VS Code.
2. Enter a Microsoft work account.
3. Continue to the corporate certificate authentication step.

## Actual result
The POST request to `https://t72f988bf86f141af91ab2d7cd011db47.certauth.login.microsoftonline.com/.../certauth` fails with `net::ERR_TIMED_OUT`. The page changes to `chrome-error://chromewebdata/`, and Windows Hello/fingerprint is never offered.

## Expected result
The integrated browser should complete Microsoft certificate authentication or hand off to Windows Hello.

## Additional information
Native Microsoft Edge on the same Windows computer and network completes the same authentication successfully using Windows Hello/fingerprint. The failure is limited to the VS Code integrated browser used by GitHub Copilot Chat. No credentials, cookies, tokens, or certificate data are attached.

### Issue Details

Item|Value
---|---
Issue Category|Bug
Target|Visual Studio Code
VS Code Version|Code 1.136.1 (a44adf7f53e00964ab890f9f8758a334f1fc15bc, 2026-09-03T05:06:41Z)
OS Version|Windows_NT x64 10.0.26200

### Additional Issue Data

[issue-data.md](https://github.com/user-attachments/files/31910670/issue-data.md)