Introduce explicit associated/unassociated pixel conversion APIs across `IPixel` and `PixelOperations`, and rework associated-alpha operations to use representation-aware bulk hooks. Update pixel implementations, converters, blenders, and generated code to consistently apply `Premultiply`/`UnPremultiply` semantics, plus SIMD-backed conversion paths for half and signed formats.
Fix codec and processing behavior where alpha handling was incorrect or lossy (notably TIFF/EXR decode/encode, convolution/resize/filter/normalization/dithering paths), and add targeted tests for these cases. Expand AOT compiler roots (including EXR and additional pixel/processor coverage), add a new public API test project for pixel-operations extensibility, and add broad alpha-representation and quantization regression coverage.
James Jackson-South