Sync Suno MCP with latest Docs OpenAPI spec

[Copilot]

The upstream Docs changed the Suno OpenAPI contract. This updates the Suno MCP implementation to match the current request schemas and async task response behavior.

• Request schema alignment

  • Treat lyric_prompt as a string, matching /suno/audios.
  • Stop adding async: true to /suno/mp4, which only accepts audio_id.
  • Make name optional for /suno/voices; only audio_url is required.

• Response handling

  • Add task polling guidance for /suno/style responses.
  • Add task polling guidance for /suno/voices responses.

• Regression coverage

  • Added focused tests for the updated Suno payloads and task-response formatting.

Example payload change:

await suno_generate_custom_music(
    lyric="",
    lyric_prompt="A nostalgic song about winter",
)

• Fixes sync: update from Docs (dacd92d docs: sync from PlatformBackend [automated]) #605