bug: mcpServers in agent doesn't support SSE server transport

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macos

### Expected behaviour

I'd like to add mcp server with SSE for an agent, such as
```
"mcpServers": {
"my-first-mcp": {
"url": "http://localhost:8080/sse",
"timeout": 60000
}
}
```
But it complains that `command` is required. In the `agent-v1.json` file, [command is required](https://github.com/aws/amazon-q-developer-cli/blob/main/schemas/agent-v1.json#L87-L89).

### Actual behaviour

But it complains that `command` is required. In the `agent-v1.json` file, [command is required](https://github.com/aws/amazon-q-developer-cli/blob/main/schemas/agent-v1.json#L87-L89).

### Steps to reproduce

_No response_

### Environment

```yaml

```

まず、リンク先のコマンド定義にある schemas/agent-v1.json を読み、mcpServers に対するエージェント設定の処理と比較します。示されている URL 設定でバリデーションエラーを再現し、既存のトランスポートサポートを追跡します。エージェントが command を要求せずに SSE MCP サーバーを受け入れて使用できれば完了です。

索引モデルが issue の本文から書いたものです。