Unactionable message when github-mcp-server is disable in Azure Dev Ops repository

### Describe the bug

We made changes to the CLI so that when you run it from inside a repository that is connected to an Azure DevOps remote we don't enable the built in GitHub MCP Server and instead print this message to the timeline:

● Detected Azure DevOps repository. GitHub MCP server has been disabled. Use /mcp enable github-mcp-server to re-enable.

However, if you run `/mcp enable github-mcp-server`, this doesn't actually work:

✗ Server "github-mcp-server" not found. Use /mcp to open the MCP server list.

### Affected version

v0.0.411

### Steps to reproduce the behavior

1. Start copilot in a repository with an AzDo remote so the above message triggers.
2. Run /mcp enable github-mcp-server

### Expected behavior

The server should be enabled, instead of an error being printed.

### Additional context

_No response_