<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Improved input validation and error reporting for chat messages, attachments, and embeddings, with clearer error messages for invalid inputs.
- Enhanced support for multimodal messages, including attachments such as images or audio.
- **Refactor**
- Unified and streamlined parameter validation across AI providers, resulting in more consistent behavior and error handling.
- Centralized parameter checks into a common provider layer, removing duplicate validation code from individual AI providers.
- **Tests**
- Simplified and consolidated audio transcription test stubs for better maintainability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
fix AI-4
fix AI-18
better provider/model choose to allow fallback to similar models (e.g., self-hosted) when the provider is not fully configured
split functions of different output types
darkskygit