v0.4.2

Added

• JPEG coefficient extraction and encoding API for steganography support:
  • Image.extractCoefficients() - Extract quantized DCT coefficients from JPEG images
  • Image.encodeFromCoefficients() - Re-encode JPEG from modified coefficients
  • JPEGFormat.extractCoefficients() - Format-specific coefficient extraction
  • JPEGFormat.encodeFromCoefficients() - Format-specific coefficient encoding
  • JPEGDecoder now supports extractCoefficients option to store quantized values
  • JPEGEncoder.encodeFromCoefficients() - Encode pre-quantized DCT coefficients
  • New types: CoefficientData, JPEGQuantizedCoefficients, JPEGComponentCoefficients
  • Comprehensive tests for coefficient extraction and encoding in
    test/formats/jpeg_coefficients.test.ts

Fixed

• Documentation: Added browser support notes to README.md and docs/src/index.md to clarify
  in-browser support.