docs: Add CHANGELOG and update documentation for v4.2.3

- Create CHANGELOG.md with release history
- Update SDK documentation with test coverage and type safety info
- Highlight 99 integration/unit tests and comprehensive coverage
- Add quality assurance badges (mypy, ruff)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,67 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [4.2.3] - 2025-01-07
+
+### Added
+- Comprehensive test coverage for `delete_objects_recursive()` method with 19 thorough tests
+- Tests cover delta suffix handling, error/warning aggregation, statistics tracking, and edge cases
+- Better code organization with separate `client_models.py` and `client_delete_helpers.py` modules
+
+### Fixed
+- Fixed all mypy type errors using proper `cast()` for type safety
+- Improved type hints for dictionary operations in client code
+
+### Changed
+- Refactored client code into logical modules for better maintainability
+- Enhanced code quality with comprehensive linting and type checking
+- All 99 integration/unit tests passing with zero type errors
+
+### Internal
+- Better separation of concerns in client module
+- Improved developer experience with clearer code structure
+
+## [4.2.2] - 2024-10-06
+
+### Fixed
+- Add .delta suffix fallback for `delete_object()` method
+- Handle regular S3 objects without DeltaGlider metadata
+- Update mypy type ignore comment for compatibility
+
+## [4.2.1] - 2024-10-06
+
+### Fixed
+- Make GitHub release creation non-blocking in workflows
+
+## [4.2.0] - 2024-10-03
+
+### Added
+- AWS credential parameters to `create_client()` function
+- Support for custom endpoint URLs
+- Enhanced boto3 compatibility
+
+## [4.1.0] - 2024-09-29
+
+### Added
+- boto3-compatible client API
+- Bucket management methods
+- Comprehensive SDK documentation
+
+## [4.0.0] - 2024-09-21
+
+### Added
+- Initial public release
+- CLI with AWS S3 compatibility
+- Delta compression for versioned artifacts
+- 99%+ compression for similar files
+
+[4.2.3]: https://github.com/beshu-tech/deltaglider/compare/v4.2.2...v4.2.3
+[4.2.2]: https://github.com/beshu-tech/deltaglider/compare/v4.2.1...v4.2.2
+[4.2.1]: https://github.com/beshu-tech/deltaglider/compare/v4.2.0...v4.2.1
+[4.2.0]: https://github.com/beshu-tech/deltaglider/compare/v4.1.0...v4.2.0
+[4.1.0]: https://github.com/beshu-tech/deltaglider/compare/v4.0.0...v4.1.0
+[4.0.0]: https://github.com/beshu-tech/deltaglider/releases/tag/v4.0.0

docs/sdk/README.md

@@ -101,6 +101,8 @@ client.put_object(Bucket='mybucket', Key='myfile.zip', Body=data)
 - **Data Integrity**: SHA256 verification on every operation
 - **Transparent**: Works with existing tools and workflows
 - **Production Ready**: Battle-tested with 200K+ files
+- **Thoroughly Tested**: 99 integration/unit tests with comprehensive coverage
+- **Type Safe**: Full mypy type checking, zero type errors
 
 ## When to Use DeltaGlider