- Updated CHANGELOG.md with complete feature list including:
  * Claude OAuth2 provider with PKCE flow and automatic token refresh
  * Response caching with semantic deduplication (Memory/Redis/SQLite/MySQL)
  * Model embeddings cache with multiple backends
  * User-specific API endpoints and MCP enhancements
  * Adaptive rate limiting and token usage analytics
  * Smart request batching and streaming optimization
  * All performance features and bug fixes

- Enhanced README.md with:
  * Claude OAuth2 authentication section with setup guide
  * Response caching details with all backends and deduplication
  * Flexible caching system with Redis/MySQL/SQLite/File/Memory
  * Updated key features with expanded descriptions
  * Configuration examples for all caching systems

- Updated DOCUMENTATION.md with:
  * Claude Code provider in Provider Support section
  * Enhanced provider descriptions with caching capabilities
  * Reference to Claude OAuth2 setup documentation

- Enhanced CLAUDE_OAUTH2_SETUP.md with key features list

- Added clarifying comments to aisbf/claude_auth.py

All documentation now accurately reflects the codebase with complete
coverage of caching systems (response cache and model embeddings cache),
request deduplication via SHA256, and all implemented features.