Fix source-generator package delivery and preview restore (Roslyn packaging)

[marcschier]

Failure

The source-generator projects disabled normal build-output packing without adding
their analyzer assemblies and private runtime closure back to the NuGet payload.
Debug and Release packages also shared IDs, and both preview workflows passed the
unsupported --configuration option to dotnet restore.

Fix

• Package each generator and its private runtime closure under
  analyzers/dotnet/cs, excluding Roslyn host assemblies and package dependencies.
• Preserve Roslyn compile references for project-reference test consumers.
• Give Debug generator packages .Debug IDs.
• Validate package contents and clean net10 consumers in both preview pipelines.
• Remove invalid restore configuration arguments from both preview workflows.

Reference

• Roslyn analyzer packaging and MSBuild restore semantics; no normative OPC UA change.
• Split from Harden security and reliability across the OPC UA stack #4021.

Tests

• Opc.Ua.SourceGeneration.Tests: 68 passed on net10.0 and 68 on net48.
• Opc.Ua.SourceGeneration.Stack.Tests: 90 passed on net10.0 and 87 on net48.
• Generated preview-pack.slnx and restored it with --disable-parallel.
• Packed both Release generators with --no-build; package-content checks and two clean net10 consumer builds passed with zero warnings/errors.

[Copilot]

Pull request overview

Note

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Fixes Roslyn source-generator NuGet packaging and preview restore behavior so generator analyzers and their private runtime closure are correctly delivered, with deterministic Debug/Release package IDs and pipeline validation.

Changes:

• Adds a shared MSBuild .targets to package generator assemblies + private runtime closure under analyzers/dotnet/cs while suppressing dependencies.
• Updates generator projects to use .Debug PackageIds and imports the new packaging targets.
• Fixes preview restore invocation and adds CI validation that inspects packages and builds clean net10 consumers.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tools/Opc.Ua.SourceGeneration/SourceGeneratorPackaging.targets	Introduces custom packing logic for analyzer payload + runtime closure.
tools/Opc.Ua.SourceGeneration/Opc.Ua.SourceGeneration.csproj	Adds Debug PackageId suffix and hooks in packaging targets / analyzer metadata.
tools/Opc.Ua.SourceGeneration.Stack/Opc.Ua.SourceGeneration.Stack.csproj	Same packaging/Debug PackageId updates for Stack generator.
.github/workflows/preview-publish.yml	Removes invalid restore args; adds package validation step.
.azurepipelines/validate-source-generator-packages.ps1	New script to validate nupkg contents and build clean consumers.
.azurepipelines/preview.yml	Removes invalid restore args; adds validation task in Release preview.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.54%. Comparing base (70c74e7) to head (80de016).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4041      +/-   ##
==========================================
- Coverage   73.55%   73.54%   -0.01%     
==========================================
  Files        1345     1345              
  Lines      180036   180038       +2     
  Branches    31677    31678       +1     
==========================================
- Hits       132427   132417      -10     
- Misses      36911    36915       +4     
- Partials    10698    10706       +8     

see 26 files with indirect coverage changes

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