Desktop app (Windows): enabling remote control fails with "Failed to set up remote session" — log shows "No authentication token available; remote export disabled"

The issue is in the remote module's authentication token lookup, likely in a Rust file like remote/shared_api.rs. Start by examining the log warning 'No authentication token available; remote export disabled' and trace where the token is fetched from (CLI config vs. desktop app credentials). Check the startup sequence for 'server policy fetch skipped' and see how the app's sign-in is registered. Verify the token flow by comparing with other working contexts like the GitHub MCP server. 'Done' is when remote control can be enabled using the app's existing sign-in.

Describe the bug

In the GitHub Copilot desktop app on Windows, remote control can't be turned on for a session. Every attempt fails with:

Remote control unavailable

Failed to update remote control: RPC error -32603: Request session.remote.enable failed with message: Failed to set up remote session. Ensure the working directory is a GitHub repository and you are authenticated.

The working directory is a GitHub repository and the app is signed in. The runtime log shows the same warning at startup and on each enable attempt:

[WARNING] [rust:remote::shared_api] No authentication token available; remote export disabled

The app has a working GitHub token in other contexts. Inside the session, gh auth status succeeds (logged in via GH_TOKEN, scopes include repo, workflow, read:org), and the GitHub MCP server connects without problems. The remote module seems to be the only part that can't get a token.

Affected version

Desktop app runtime version 1.0.87-0. The standalone copilot CLI is not installed on this machine.

Steps to reproduce the behavior

1. Open a worktree session in the desktop app for a GitHub-hosted repo (origin is https://github.com/<owner>/<repo>.git).
2. Try to turn on remote control for the session, to manage it from GitHub Mobile.
3. The "Remote control unavailable" error above appears.
4. ~\.copilot\logs\process-*.log shows No authentication token available; remote export disabled at the time of the attempt.

Things that did not help:

• Restarting the app
• Signing out and back in to the app
• Pushing the session branch to origin and setting upstream tracking

Expected behavior

Remote control turns on and the session can be managed from GitHub Mobile, using the app's existing GitHub sign-in.

Additional context

• OS: Windows 11 Home, x86_64 (AMD64)
• Windows Credential Manager has a ...github-copilot-app entry (the app's sign-in), but there's no standalone Copilot CLI sign-in entry.
• ~\.copilot\config.json has no logged_in_users or last_logged_in_user.
• At startup the log also shows server policy fetch skipped: no authenticated GitHub host available before the account is picked up later.
• Hypothesis: the remote module looks for the CLI's own stored sign-in instead of the credential the desktop app registers, so it finds no token. Possibly related: #4905, #4409.