Add Anthropic/OpenAI Provider Support

Added

• OpenAI Provider Support: Full integration with OpenAI API through dialectus-engine 0.4.0

  • Configure debates using OpenAI models (GPT-4, GPT-3.5, etc.)
  • Automatic API key validation at startup
  • Support for OPENAI_API_KEY environment variable

• Anthropic Provider Support: Full integration with Anthropic Claude models through dialectus-engine 0.4.0

  • Configure debates using Claude models (Claude 3.5 Sonnet, Claude 3 Opus, etc.)
  • Automatic API key validation at startup
  • Support for ANTHROPIC_API_KEY environment variable
  • Added example configuration for Anthropic debates

• Provider Key Validation: Enhanced startup checks to validate API keys before running debates

  • Clear error messages when required API keys are missing
  • Prevents debates from failing midway due to authentication issues

Changed

• Updated Engine Dependency: Now requires dialectus-engine >= 0.4.0

  • Benefits from improved provider architecture
  • Access to new OpenAI and Anthropic providers
  • Enhanced cost tracking and rate limiting

• Configuration Improvements: Better handling of provider-specific configuration

  • More robust config validation
  • Clearer error messages for misconfigured providers

• Documentation: Significantly expanded README with provider setup instructions

  • Detailed setup guides for all supported providers (Ollama, OpenRouter, OpenAI, Anthropic)

• Virtual Environment: Switched to .venv as the standard virtual environment directory

  • Aligns with modern Python tooling conventions (uv, etc.)

Fixed

• Character Encoding: Fixed cp1252 encoding issues on Windows systems
  • Improved handling of Rich library output on different platforms

Testing

• Enhanced Test Coverage: Added new tests for provider validation
  • Tests for API key validation logic
  • Tests for provider-specific configuration handling