Authentication fails on WSL despite correct environment and localhost networking

The Copilot for Vim extension fails to complete the authentication process on my WSL (Ubuntu 24.04) setup. The authentication is successful in the browser, but the callback to Vim never completes, and Vim remains stuck on the "Waiting..." message.

I have performed this troubleshooting and can confirm the issue is not with my local environment.

Symptom:

Running :Copilot setup provides a code.
Authenticating in a browser (running inside WSL) succeeds with the "Congratulations, you're all set!" message.
Vim remains stuck on "Waiting (could take up to 5 seconds)" and never receives the authentication confirmation.
Troubleshooting Steps Performed:

Plugin Version: The issue occurs on both the latest version and after downgrading to v1.41.0.
WSL-Native Browsers: The issue occurs with multiple browsers installed and running directly within WSL, including:
Firefox (installed via Snap)
Google Chrome (non-Snap Deb version)
Firewall: Confirmed that ufw is not installed or active.
Localhost Networking Test: I have confirmed that basic localhost communication within WSL is working perfectly. A Python http.server can be successfully reached from curl via localhost.
This testing suggests the issue is a bug within the Copilot agent's internal web server or its callback handling mechanism within a WSL environment.

My Environment:

OS: Windows 11
WSL Version: WSL 2
Linux Distribution: Ubuntu 24.04 LTS
Vim Version: 9.1
Node Version (in wsl): 22.16.0
Copilot Status after hang and restart: Copilot: Not authenticated. Invoke :Copilot setup (process then repeats)

(Above is AI generated)

Comece pela implementação por trás de :Copilot setup e pelo callback de autenticação que deixa o Vim exibindo "Waiting...". Reproduza o fluxo no WSL 2 com as versões informadas do Ubuntu, Vim e Node, usando os detalhes do teste de localhost como contexto. Está concluído quando a autenticação do navegador é concluída, o callback chega ao Vim e o Copilot informa um estado autenticado.

Escrita pelo modelo de indexação a partir do texto da issue.