Add a new extension that provides automatic text-to-speech for chat
responses using ElevenLabs API.
Features:
- `speak` tool for converting text to voice messages
- RPC methods: tts.status, tts.enable, tts.disable, tts.convert
- User preferences file for persistent TTS state
- Configurable voice ID, model, and max text length
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
