[Bug] MCP settings shows no servers although user config APIs return enabled servers

### Short summary

After upgrading and restarting the GitHub Copilot app, **Settings > MCP servers** shows **"No servers configured"**, even though user-level MCP configuration is intact and the configured servers remain available to sessions.

This may be related to #2838, but this report includes a reproducible case on v1.1.10 where the bundled SDK can read and discover the servers successfully while the settings UI renders an empty list.

### Affected version or release

- GitHub Copilot app: 1.1.10
- Bundled Copilot CLI runtime: 1.0.80
- OS: Windows

### What happened?

The MCP settings page reports that no servers are configured.

Independent checks using the app's bundled SDK show:

- `mcp.config.list`: 5 user-configured servers
- `mcp.discover`: 5 servers
- Source: `user`
- Enabled: `true` for all 5

Each of the five configured MCP servers was also tested with a real, read-only tool call and responded successfully. The issue therefore appears limited to the settings UI's configured-server list rather than configuration loss or MCP runtime failure.

Server names, URLs, credentials, and tool response data are intentionally omitted.

### Steps to reproduce

1. Configure multiple user-level MCP servers for Copilot CLI / the GitHub Copilot app.
2. Confirm they are available and functioning.
3. Upgrade to GitHub Copilot app v1.1.10 and restart the app.
4. Open **Settings > MCP servers**.
5. Observe **"No servers configured"**.
6. Query the same runtime through the bundled SDK using `mcp.config.list` and `mcp.discover`.
7. Observe that both APIs still return the enabled user servers.

### Expected behavior

The MCP settings page should list the same user-configured servers returned by `mcp.config.list` / `mcp.discover`, including their enabled and connection state.

### Additional context

- The user-level MCP configuration file remains valid and unchanged.
- No configured servers are marked disabled.
- No enterprise MCP policy is filtering these servers.
- Restarting the app did not restore the list.
- The configured MCP tools remain usable from sessions despite the empty settings page.

Start at Settings > MCP servers and trace how the UI obtains its configured-server list; compare it with the bundled SDK calls mcp.config.list and mcp.discover. Done means the page lists the same enabled user servers and shows their enabled and connection state, while existing sessions continue to use them.

索引モデルが issue の本文から書いたものです。