feat(HdrHistogram#105): Remove EOL target frameworks from Benchmarking project (HdrHistogram#113)

* plan(HdrHistogram#105): initial brief from issue

* plan(HdrHistogram#105): review brief

* plan(HdrHistogram#105): apply brief review feedback

* plan(HdrHistogram#105): review brief

* plan(HdrHistogram#105): create task breakdown

* feat(HdrHistogram#105): implement tasks

* feat(HdrHistogram#105): complete implementation

Author: leecampbell-codeagent

HdrHistogram.Benchmarking/HdrHistogram.Benchmarking.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>net8.0;net7.0;net6.0;net5.0;net47;netcoreapp3.1;netcoreapp2.1.29</TargetFrameworks>
+    <TargetFrameworks>net8.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>

spec/tech-standards/build-system.md

@@ -38,10 +38,10 @@ HdrHistogram.sln
 
 ### Benchmarking Project
 
-Multi-targeted for performance comparison:
+Targets the current LTS runtime only (developer tool, not a shipped library):
 
 ```xml
-<TargetFrameworks>net8.0;net7.0;net6.0;net5.0;net47;netcoreapp3.1;netcoreapp2.1.29</TargetFrameworks>
+<TargetFrameworks>net8.0</TargetFrameworks>
 ```
 
 ## Dependencies
@@ -224,7 +224,7 @@ dotnet run -c Release -- -f *Recording*
 ### Benchmark Configuration
 
 BenchmarkDotNet is used with these targets:
-- Multiple .NET versions for comparison
+- `net8.0` (current LTS runtime)
 - Windows diagnostics support
 - Memory allocation tracking