Remove leftover .orig files and fix stray lowercase MoBi.R paths

Cleanup of artifacts flagged during the #2441 review:
- Delete merge-leftover .orig files (RunActiveSimulationCommand.cs.orig,
  ProjectTaskSpecs.cs.orig) that still contained conflict markers.
- Correct the wrong-case "src\Mobi.R" project paths in MoBi.sln and
  MoBi.R.Tests.csproj to "src\MoBi.R", and drop the duplicate
  src/Mobi.R/Domain/SimulationCreationResult.cs it produced. These are
  distinct paths on case-sensitive (Linux) CI.

Author: rwmcintosh

MoBi.sln

@@ -42,7 +42,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MoBi.CLI", "src\MoBi.CLI\Mo
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MoBi.CLI.Core", "src\MoBi.CLI.Core\MoBi.CLI.Core.csproj", "{8D21EB6A-9F65-4AD0-9D91-8C94195EE121}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MoBi.R", "src\Mobi.R\MoBi.R.csproj", "{259DA791-3352-4BFA-AB42-BE0F07621FFF}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MoBi.R", "src\MoBi.R\MoBi.R.csproj", "{259DA791-3352-4BFA-AB42-BE0F07621FFF}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MoBi.R.Tests", "tests\MoBi.R.Tests\MoBi.R.Tests.csproj", "{FC91836B-185D-40A8-A483-8B515D4C49BE}"
 EndProject

src/MoBi.Presentation/UICommand/RunActiveSimulationCommand.cs.orig

@@ -31,7 +31,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\src\MoBi.Core\MoBi.Core.csproj" />
-    <ProjectReference Include="..\..\src\Mobi.R\MoBi.R.csproj" />
+    <ProjectReference Include="..\..\src\MoBi.R\MoBi.R.csproj" />
     <ProjectReference Include="..\MoBi.HelpersForTests\MoBi.HelpersForTests.csproj" />
   </ItemGroup>