Create unified provider abstraction layer for direct LLM integrations beyond
HTTP specs, inspired by FuzzyAI's comprehensive provider system.
- Add BaseLLMProvider abstract class with standard interface (generate, chat,
sync_generate, sync_chat methods)
- Implement OpenAIProvider supporting chat completions API
- Implement AnthropicProvider supporting messages API
- Create provider factory for instantiation by name (create_provider,
get_provider_class)
- Add 60 unit tests covering all provider implementations