OX-02: create the VSIX container (import Microsoft.VsSDK.targets, as Snipper's SDK-style project does)

The first Windows CI run built Owen.VisualStudio.dll but no .vsix: an SDK-style project
gets no VSIX packaging from the build tools package alone. The build step now fails
loudly when no .vsix is produced.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011ZFvhLx1fM9Gerg4dKsZcL

Author: claude

.github/workflows/ci.yml

@@ -3548,7 +3548,9 @@ jobs:
           $msbuild = & $vswhere -latest -products * -requires Microsoft.Component.MSBuild -find "MSBuild\**\Bin\MSBuild.exe" | Select-Object -First 1
           & $msbuild frontend\roslyn\Owen.VisualStudio\Owen.VisualStudio.csproj /restore /p:Configuration=Release /p:DeployExtension=false /v:m
           if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
-          Get-ChildItem -Recurse frontend\roslyn\Owen.VisualStudio -Filter *.vsix | ForEach-Object { $_.FullName }
+          $built = @(Get-ChildItem -Recurse frontend\roslyn\Owen.VisualStudio -Filter Owen.VisualStudio.vsix)
+          if ($built.Count -eq 0) { Write-Error "no Owen.VisualStudio.vsix was produced"; exit 1 }
+          $built | ForEach-Object { "$($_.FullName) ($($_.Length) bytes)" }
       - name: The acceptance in Visual Studio
         shell: powershell
         run: |

frontend/roslyn/Owen.VisualStudio/Owen.VisualStudio.csproj

@@ -30,6 +30,18 @@
     <CopyOutputSymbolsToOutputDirectory>true</CopyOutputSymbolsToOutputDirectory>
     <TargetVsixContainerName>Owen.VisualStudio.vsix</TargetVsixContainerName>
     <VSSDKBuildToolsAutoSetup>true</VSSDKBuildToolsAutoSetup>
+    <TargetVsixContainer>$(MSBuildProjectDirectory)\bin\$(Configuration)\$(TargetFramework)\$(TargetVsixContainerName)</TargetVsixContainer>
+    <CreatePkgDefAssemblyToProcess>$(MSBuildProjectDirectory)\obj\$(Configuration)\$(TargetFramework)\$(AssemblyName).dll</CreatePkgDefAssemblyToProcess>
+    <!-- the VSSDK's intermediate layout, spelled out for an SDK-style project (as Snipper does) -->
+    <VsixIntermediateOutputPath>$(BaseIntermediateOutputPath)$(Configuration)\$(TargetFramework)\vsix\</VsixIntermediateOutputPath>
+    <IntermediateVsixManifest>$(VsixIntermediateOutputPath)extension.vsixmanifest</IntermediateVsixManifest>
+    <FileManifest>$(VsixIntermediateOutputPath)files.json</FileManifest>
+    <TemplateFileManifest>$(VsixIntermediateOutputPath)templateFiles.json</TemplateFileManifest>
+    <ResourceManifest>$(VsixIntermediateOutputPath)resources.json</ResourceManifest>
+    <CtoFileManifest>$(VsixIntermediateOutputPath)ctoFiles.json</CtoFileManifest>
+    <CtoCacheFile>$(VsixIntermediateOutputPath)mergeCto.cache</CtoCacheFile>
+    <CreateTemplateManifestsCacheFile>$(VsixIntermediateOutputPath)createTemplateManifests.cache</CreateTemplateManifestsCacheFile>
+    <TemplateOutputDirectory>$(VsixIntermediateOutputPath)</TemplateOutputDirectory>
     <!-- the service client runs on its own threads by design (never the UI thread); the
          analyzers that assume a JoinableTaskFactory context everywhere do not apply to it -->
     <NoWarn>$(NoWarn);VSTHRD003;VSTHRD010;VSTHRD100;VSTHRD110;VSTHRD200;VSSDK007</NoWarn>
@@ -53,4 +65,14 @@
   <ItemGroup>
     <None Include="source.extension.vsixmanifest" SubType="Designer" />
   </ItemGroup>
+  <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets"
+          Condition="'$(OS)' == 'Windows_NT' and '$(VSToolsPath)' != '' and Exists('$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets')" />
+
+  <Target Name="OwenVsixIntermediate" BeforeTargets="DetokenizeVsixManifestFile;GenerateFileManifest"
+          Condition="'$(OS)' == 'Windows_NT'">
+    <MakeDir Directories="$(VsixIntermediateOutputPath)" />
+  </Target>
+
+  <Target Name="OwenCreateVsix" AfterTargets="Build" DependsOnTargets="CreateVsixContainer"
+          Condition="'$(OS)' == 'Windows_NT'" />
 </Project>