fix: disable parallel builds for all Integration.Tests projects

Add BuildInParallel=false to SimpleProject and DisabledProject references
in addition to MultiTargetProject. This ensures all Integration.Tests
projects build sequentially to prevent concurrent access to the shared
CycloneDX.MSBuild dependency.

Without this, SimpleProject and DisabledProject can build in parallel
with MultiTargetProject's inner framework builds, causing multiple
simultaneous attempts to write CycloneDX.MSBuild.deps.json.

Build order is now strictly sequential:
1. CycloneDX.MSBuild
2. SimpleProject
3. MultiTargetProject (net6.0, net8.0, netstandard2.0 - also sequential)
4. DisabledProject
5. Test project

This fixes the macOS CI build failure with deps.json file locking.

Author: claude

tests/CycloneDX.MSBuild.Tests/CycloneDX.MSBuild.Tests.csproj

@@ -34,16 +34,18 @@
     </ProjectReference>
 
     <!-- Reference the test projects to ensure they're built before copying -->
+    <!-- Disable parallel builds to prevent file locking on shared CycloneDX.MSBuild dependency -->
     <ProjectReference Include="../Integration.Tests/SimpleProject/SimpleProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+      <BuildInParallel>false</BuildInParallel>
     </ProjectReference>
-    <!-- MultiTargetProject builds for 3 frameworks - prevent parallel builds to avoid file locking -->
     <ProjectReference Include="../Integration.Tests/MultiTargetProject/MultiTargetProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
       <BuildInParallel>false</BuildInParallel>
     </ProjectReference>
     <ProjectReference Include="../Integration.Tests/DisabledProject/DisabledProject.csproj">
       <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+      <BuildInParallel>false</BuildInParallel>
     </ProjectReference>
   </ItemGroup>