Refactor SPMD job system, add GGX mipmap benchmark

- Replace IJobSPMD with T4-generated, multi-type SPMD job interfaces and wrappers (up to 8 numeric types)
- Extend ISPMD with Cast/BitCast; implement for ScalarLane and WideLane (SIMD-aware)
- Add unary minus, scalar-lane, and lane-scalar operators to Vector2/3/4; improve Select methods
- WideLane now partial with T4-generated Cast/BitCast (SIMD conversions)
- SPMD job Execute now requires unmanaged TLane; update all usages and benchmarks
- Add GGXMipGenerationBenchmark with vectorized and scalar paths, SkiaSharp output
- Update project files: add generated code, SkiaSharp, bump version to 1.3.0
- Misc: fix formatting, method signatures, FreeList logic

Misaki.HighPerformance.Test/Benchmark/SPMDBenchmark.cs

@@ -36,7 +36,7 @@ public unsafe class SPMDBenchmark
             height = _SIZE,
         };
 
-        var handle = _scheduler.ScheduleParallelSPDM<Jobs.NoiseJobMathSPMD, float>(ref job, _SIZE * _SIZE, 64, false);
+        var handle = _scheduler.ScheduleParallelSPDM<Jobs.NoiseJobMathSPMD, float>(ref job, _SIZE * _SIZE, 64, false, JobPriority.Normal);
         _scheduler.Wait(handle);
     }