SLNX: "Do not build" (no <build> node) is always reset

A .slnx solution contains a WiX project. By default, this WiX project should not be built. The configuration via Visual Studio is possible without any problems. However, if the solution is reopened, the configuration is reset and the Wix project is set to built again.

Reproduction:

Microsoft Visual Studio Professional 2022 (64-bit), Version 17.14.18 (October 2025)
Test Solution: TestSLNX.zip

1. Disable Build of WiX project
   
2. Correct SLNX is generated

<Solution>
  <Configurations>
    <Platform Name="x64" />
  </Configurations>
  <Project Path="TestApp/TestApp.csproj">
    <Platform Project="x64" />
  </Project>
  <Project Path="TestWix/TestWix.wixproj" Id="4a922bd5-487a-4024-ab28-b9d5576c9993" />
</Solution>

3. Close Solution in Visual Studio and reopen it.
4. Click "Save all" without changing anything.
5. A <Build /> node has been added and building has been activated again.

<Solution>
  <Configurations>
    <Platform Name="x64" />
  </Configurations>
  <Project Path="TestApp/TestApp.csproj">
    <Platform Project="x64" />
  </Project>
  <Project Path="TestWix/TestWix.wixproj" Id="4a922bd5-487a-4024-ab28-b9d5576c9993">
    <Build />
  </Project>
</Solution>

Start by opening the attached TestSLNX.zip in Visual Studio and reproducing the save-after-reopen sequence. Trace the solution persistence path for a project without a node; done means reopening and saving preserves the omitted node and does not re-enable building.