feat: Add LLM provider adapter documentation and examp

[dgenio]

Summary

This PR addresses #235 by providing comprehensive documentation and examples for creating adapters that convert MCP tool schemas to various LLM provider formats (Gemini, OpenAI, Claude).

Changes

• New documentation page (docs/llm-adapters.md): Comprehensive guide covering:

  • Basic adapter patterns
  • Complete implementations for Gemini, OpenAI, and Anthropic Claude
  • Advanced schema transformations (nested objects, arrays, enums)
  • Error handling patterns
  • Best practices

• Runnable example (examples/snippets/clients/llm_adapter_example.py): Demonstrates:

  • Connecting to MCP servers
  • Listing and converting tools
  • Batch conversion with error handling
  • Validation utilities

• Documentation updates: Added references in:

  • docs/index.md - Getting Started section
  • README.md - Advanced Usage and Documentation sections
  • mkdocs.yml - Navigation menu

Design Decision

Following maintainer feedback, this PR provides documentation and examples rather than official adapter utilities. This approach:

• Makes it easy for developers to create adapters
• Avoids maintenance burden of third-party SDK dependencies
• Provides clear patterns and best practices
• Includes working examples for all three major providers

Testing

• ✅ All files pass linting (ruff, pyright)
• ✅ Documentation follows mkdocs format
• ✅ Example script is registered and runnable
• ✅ No breaking changes (documentation only)

Related

Closes #235