WebFetchRedirectError: Redirects are not followed for OpenAI documentation URLs

### Describe the bug

When trying to fetch content from certain OpenAI documentation URLs, the tool fails with a WebFetchRedirectError instead of following the 301 redirect.

### Affected version

GitHub Copilot CLI 1.0.64-3.

### Steps to reproduce the behavior

1. Use a tool to fetch https://platform.openai.com/docs/guides/realtime
2. Observe the WebFetchRedirectError 301 redirect failure.

### Expected behavior

The tool should automatically follow 301 redirects to the updated documentation URLs (e.g., https://developers.openai.com/...).

### Additional context

_No response_

Search the CLI for WebFetchRedirectError and trace the WebFetch HTTP request path, then reproduce the failure with the listed platform.openai.com URL. Verify the tool follows the 301 redirect to the corresponding developers.openai.com documentation URL, and run any nearby fetch tests or add coverage if the repository provides them.

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