SPMD API overhaul: gather/scatter, job & packaging updates

- ISPMDLane: add MaskGather, MaskStore, Scatter, MaskScatter; update MaskLoad/Gather signatures for hardware parity
- WideLane/ScalarLane: implement new methods with HW/fallback logic
- MathV: gather/mask-gather now delegate to lane methods
- Vector2/3/4: add CompressStore, Scatter, MaskScatter
- SPMD jobs/tests/README: migrate to new APIs for correctness
- Use Unsafe.BitCast instead of Unsafe.As/AsRef
- Add SPMDUtility for gather index extraction
- Job system: add ICustomJob<TSelf>, ScheduleCustom overload
- FreeList concurrency obsolete; always thread-safe
- NuGet: include LICENSE/README, set license/readme in .csproj
- Docs: update SPMD usage, clarify safety notes
- Minor: doc fixes, CompressStore test improvements

Misaki.HighPerformance.Mathematics.CodeGen/Generators/VectorGenerator.cs

@@ -217,6 +217,7 @@ namespace Misaki.HighPerformance.Mathematics.CodeGen.Generators
             StartRegion("Constructors");
 
             sourceBuilder.AppendLine($@"
+        {INLINE_METHOD_ATTRIBUTE}
         public unsafe {typeName}(global::System.ReadOnlySpan<{componentType}> values)
         {{
             if (values.Length < {typeInfo.Row})
@@ -307,6 +308,7 @@ namespace Misaki.HighPerformance.Mathematics.CodeGen.Generators
             foreach (var (signature, assignment) in _constructorSignatures)
             {
                 sourceBuilder.Append($@"
+        {INLINE_METHOD_ATTRIBUTE}
         public {typeName}({signature})
         {{");
                 for (var i = 0; i < typeInfo.Row; i++)