Add Roslyn incremental source generator samples

[Copilot]

• Create csharp/roslyn-sdk/SourceGenerators/ folder structure
• Sample 1: Attribute-based member generator (GenerateMembersAttribute)
• Sample 2: Non-C# file to C# generator (CSV to strongly-typed class)
• Build and verify both samples
• Add unit tests for GenerateMembers source generator
  • Create GenerateMembers.Test project with xUnit + Roslyn testing infrastructure
  • Test: class with properties generates Describe() and PropertyNames
  • Test: struct with attribute generates correctly
  • Test: class without attribute produces no generated output
  • Test: class in global namespace generates without namespace block
• Add unit tests for CsvGenerator source generator
  • Create CsvGenerator.Test project with xUnit + Roslyn testing infrastructure
  • Test: CSV with headers and rows generates strongly-typed class
  • Test: CSV with only header (no data rows) produces no output
  • Test: non-CSV additional file is ignored
  • Test: CSV with three columns generates all properties
• Update solution file to include test projects
• Build and run all tests (8/8 passing)

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[agocke]

@copilot Please add unit tests

[Copilot]

@copilot Please add unit tests

Added unit tests in commit 622124b. Created two test projects:

• GenerateMembers.Test (4 tests): class with properties, struct with attribute, class without attribute (no output), and class in global namespace
• CsvGenerator.Test (4 tests): CSV with headers/rows, header-only CSV (no output), non-CSV file ignored, and CSV with three columns

All 8 tests pass using MSTest with Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.MSTest.

[agocke]

@copilot please use xunit

[Copilot]

@copilot please use xunit

Switched both test projects to xUnit in commit 5082e7f. Replaced MSTest with xunit 2.9.3 and Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit 1.1.2. All 8 tests pass.