fix: update to correct list composers response

[jspeth]

Fixes the response handling for the list command.

The response data is no longer an array. It's a dictionary containing a composers field:

{
  "composers": [
    {
      "bcId": "...",
      "createdAtMs": 1753625549554,
      ...
    }
  ],
  "didLoadStatus": true
}

This fix adds a new type ListBackgroundComposersResponse for the response. Then in the ComposerService list function, returns the response composers.

---

Summary by cubic

Updated the list function in ComposerService to handle the new response format, returning the composers array from a response object instead of a raw array.

• Types
• Added ListBackgroundComposersResponse type to match the updated API response.

[cubic-dev-ai]

cubic analysis

No issues found across 2 files. Review in cubic