Move the main target framework from net8.0 to net10.0 and the preview lane from net10.0 to net11.0, adding a global.json floor for SDK 10+ and updating CI coverage and test projects to match.
The change also adjusts hardware-intrinsic feature tests for .NET 11's x86-64-v2 baseline, updates Magick.NET, adds PDF files to LFS, and converts many internal helper and codec APIs from Span<T> to ReadOnlySpan<T> where inputs are not mutated.
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