Cloud session create times out waiting for remote sandbox CLI host

### Short summary

Cloud session creation fails every time with RPC -32603: timed out waiting for the remote sandbox CLI host to connect.

### Affected version or release

GitHub Copilot app 1.1.12 on macOS 26.6.2 (25G83)

### Installation context

GitHub Copilot desktop app. Creating a **Cloud** session against the private repository `Apex-Global-Solutions/ARWorkflow` (default branch `master`). Local/worktree sessions for the same repo work.

The original reporter uses Enterprise Managed User `FLuque_axg` (cannot file on this public repo). Filed from personal account `fabianluque`.

### What happened?

Every attempt to create a new Cloud session fails at approximately the 67-second mark. The client reports that the cloud session was created, but the remote CLI host never connects in time.

Error shown in the app:

```
Session creation failed
Failed to create session: RPC error -32603: Request session.create failed with message: Timed out waiting for the remote sandbox to start. The cloud session was created but its CLI host did not connect in time. Please try again.
```

This is 100% reproducible (every attempt).

### Steps to reproduce

1. Open the GitHub Copilot app (1.1.12) on macOS.
2. Create a new **Cloud** session targeting `Apex-Global-Solutions/ARWorkflow`.
3. Wait for session creation.

### Expected behavior

The cloud session starts and the remote CLI host connects so the session becomes usable.

### Additional context

- Timing is consistent: the error appears around **67 seconds** after starting creation.
- The remote session appears to be created; only the CLI host connection times out.
- Local / worktree sessions continue to work for the same repository.
- Repo includes `.github/workflows/copilot-setup-steps.yml` (sets up .NET from `global.json` and Node.js 20.19).
- GitHub-reported repository size is ~49 MB.
- This is a different failure from an earlier `Failed to create remote session in the cloud: 502` (GitHub Unicorn HTML page) seen on 2026-08-17 during a GitHub outage.

Reproduce the failure in GitHub Copilot app 1.1.12 on macOS using the specified private repository, and compare Cloud session creation with local/worktree sessions. Review .github/workflows/copilot-setup-steps.yml and the reported remote CLI host timeout; done means a Cloud session starts and its CLI host connects before the timeout.

索引モデルが issue の本文から書いたものです。