MCP Authorization successful messages are confusing / misleading for failed MCP authentication flows

### Describe the bug

When I authenticate to an MCP server included in one of my plugins, a browser pops up and shows an "Authorization successful" message:

Similarly, when I navigate back to the CLI, it shows me a message saying I have "successfully authenticated" to my MCP server.

However, the MCP connection failed in this case, and it is easy to miss - only shows up in the `/mcp show` command output which is easy to miss.

Is it possible to show the error message earlier in the flow, either in the browser or when navigating back to the CLI after the browser interactive authentication? This is confusing for the user and may lead them to easily miss that they have not been authenticated properly.

### Affected version

GitHub Copilot CLI 1.0.46

### Steps to reproduce the behavior

1. Install a plugin that bundles an MCP server via `/plugin install `
2. If authorization popup in browser doesn't happen automatically, run `/mcp show` and navigate to the MCP server under the plugin
3. Press "r" to re-authenticate and complete the browser-based auth flow with an account that is not authorized to simulate a failure case
4. Navigate back to the CLI and observe a successful authentication message
5. Press "enter" to notice a red X next to the MCP server, indicating MCP connection was unsuccessful despite the previous messages

### Expected behavior

I expected an error message earlier in the flow to make it clear that MCP connection failed

### Additional context

_No response_

Reproduce the flow with `/plugin install`, `/mcp show`, and the `r` re-authenticate action using an unauthorized account. Trace the browser-auth return and the CLI message shown before the MCP connection result; done means failed authentication is surfaced clearly before the red X is easy to miss.

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