Add CLAUDE.md documentation for AI assistants

[felippepestana]

Summary

This PR adds a comprehensive CLAUDE.md file that documents the codebase structure, development workflows, and conventions for AI assistants working in this repository. This serves as a companion guide to help AI tools understand the project layout, development practices, and key patterns used throughout the SDK.

Key Changes

• Added CLAUDE.md — A detailed guide covering:
  • Project overview and auto-generation notice (Stainless)
  • Complete repository structure with descriptions of each directory and key files
  • Development setup instructions (using uv and traditional pip)
  • Common development commands (linting, formatting, testing, building)
  • Code conventions including file headers, type checking, imports, and naming patterns
  • SDK-specific patterns like NOT_GIVEN sentinel, resource classes, response models, streaming, and pagination
  • Client configuration options and environment variables
  • Optional extras installation
  • Testing patterns and CI/CD workflow overview
  • Guidelines for adding new features

Notable Details

• Clearly distinguishes between auto-generated code (most of src/anthropic/) and hand-written code (src/anthropic/lib/, examples/, tests/)
• Documents the strict type-checking setup (Pyright strict mode, mypy, ruff rules)
• Explains key SDK patterns like NOT_GIVEN for optional parameters, streaming helpers, and pagination
• Provides quick reference tables for client features and CI/CD workflows
• Includes practical examples of common commands and development workflows

https://claude.ai/code/session_01UhwbQib68DeforQQQn4TPb