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.Jobs/Misaki.HighPerformance.Jobs.csproj

@@ -6,13 +6,20 @@
     <Nullable>enable</Nullable>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
-    <AssemblyVersion>3.1.5</AssemblyVersion>
+    <AssemblyVersion>3.1.6</AssemblyVersion>
     <Version>$(AssemblyVersion)</Version>
     <Authors>Misaki</Authors>
     <PackageProjectUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</PackageProjectUrl>
     <RepositoryUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</RepositoryUrl>
+    <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Include="../LICENSE" Pack="true" PackagePath=""/>
+    <None Include="README.md" Pack="true" PackagePath=""/>
+  </ItemGroup>
+
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
     <IsAotCompatible>True</IsAotCompatible>
   </PropertyGroup>