Awww...son of a crap. No idea how this happened, but Jenkins was generating falsely succeeding builds. This is an "old new" ci server (early in the config but I haven't visited it in 8 or 9 months) I had installed the MSBuild plug in but hadn't handled the config bug (you have to configure the job with the folder specified in the plug-in sans executable, but you have to go back and edit the value to point the agent to the actual executable) I also had forgotten to specify my MSBuild Agent in the project's job, but the build was succeeding on checkin. I have no idea how Jenkins was using MSBuild to build when I hadn't pointed the MSBuild plugin to the executable, but fixing this fixed the problem.
C:/server.ci/baz.inga/baz.inga.resources.sln
/t:build /p:PlatformTarget=x86 /p:Configuration=Release
...and everything builds just fine. When did Jenkins start building MSBuild straight out of the box? ...In fact, when did it start checking out of a git repository with no polling trigger? These were what really confused me.
"I need build Skynet. Plz send code"