Feature Request

Is your feature request related to a problem?
When running multiple agents (e.g., Saphira, Smaug, Sol), they all share the same TTS voice since messages.tts is global. It would be great to give each agent a distinct voice to match their persona.

Describe the solution you'd like
Add optional TTS settings per agent in agents.list[]:

{
  "id": "smaug",
  "name": "Smaug",
  "tts": {
    "voiceId": "deep-voice-id-here"
  }
}

Agent-level settings would override the global messages.tts config. Only voiceId might be needed, inheriting provider, apiKey, etc. from the global config.

Use case

• Saphira: Professional female voice
• Smaug (CFO): Deeper, authoritative voice
• Sol (Wellness): Calm, soothing voice

Additional context
Currently using ElevenLabs with Telegram. Multiple agents already have separate Telegram bot accounts, so per-agent voice would complete the persona separation.