- Migrate `compress_image.go` to `internal/imageutil` for better encapsulation.
- Reorganize LLM provider implementations into distinct packages (`google`, `openai`, and `anthropic`).
- Replace `go_llm` package name with `llm`.
- Refactor internal APIs for improved clarity, including renaming `anthropic` to `anthropicImpl` and `google` to `googleImpl`.
- Add helper methods and restructure message handling for better separation of concerns.
Introduce `Providers` struct to handle different language model providers. Implement `Parse` method to extract and validate provider/model from input string, then return a chat completion interface. Add error handling for invalid formats or unknown providers.
