fix(voice): handle cloned voices without a display name

[dvd233]

What changed

Fall back to the cloned voice_id when a cloned voice response does not include voice_name, while preserving the legacy display name when it is present.

Why

The current MiniMax Voice Management API response for voice_cloning entries provides voice_id, description, and created_time, but not voice_name. The existing formatter interpolated the missing field as Name: undefined, making cloned voices harder to identify in MCP clients.

Reference: https://platform.minimax.io/docs/api-reference/voice-management-get

Verification

• pnpm run build
• Mocked smoke check covering current and legacy voice_cloning response shapes
• git diff --check

The repository-wide pnpm run lint currently fails on the unchanged baseline formatting in all 20 source files; no formatting-only changes are included in this focused patch.

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