refactor: Improve code generation quality and fix registration bug

[ncipollina]

Summary

This PR includes code quality improvements to the source generator and a critical bug fix for registration interception.

Bug Fix: Registration Interception

Problem: The generator was intercepting ALL generic AddScoped/Transient/Singleton calls regardless of parameters, but only generating parameterless interceptor signatures. This caused silent data loss for:

• Factory delegates: AddScoped<T1, T2>(sp => new T2())
• Keyed services: AddKeyedScoped<T1, T2>("key")
• Instance registrations: AddSingleton<T1>(instance)

Solution: Added parameter count check in ClosedGenericRegistrationProvider.cs:57 to only match the parameterless overload.

Related:

• Test case: 022_FactoryDelegate_ShouldNotIntercept
• Diagnostic: DECOW020 for unsupported patterns
• Documentation: Updated with supported registration signatures
• Future work: Issue #3

Code Quality Improvements

String Escaping:

• Use SymbolDisplay.FormatLiteral instead of manual escaping
• Handles all edge cases (backslashes, quotes, newlines, unicode)
• More robust and maintainable

Namespace Verification:

• Replace string comparison with pattern matching for attribute validation
• No string allocation from ToDisplayString()
• Type-safe compile-time verification
• Added metadata name constants to AttributeNames class

Pattern matching example:

if (attr.AttributeClass is not
    {
        MetadataName: AttributeNames.GenericDecoratedByMetadataName,
        ContainingNamespace:
        {
            Name: "Attributes",
            ContainingNamespace: { Name: "DecoWeaver", ContainingNamespace.IsGlobalNamespace: true }
        }
    })
    continue;

Documentation Updates

• Updated docs/usage/open-generics.md with actual issue link (Support factory delegates, keyed services, and instance registrations #3)
• Added "Supported Registration Signatures" section
• Clear examples of what works and what doesn't

Files Changed

• src/LayeredCraft.DecoWeaver.Generators/Providers/ClosedGenericRegistrationProvider.cs - Bug fix
• src/LayeredCraft.DecoWeaver.Generators/Emit/InterceptorEmitter.cs - Better string escaping
• src/LayeredCraft.DecoWeaver.Generators/Providers/DecoratedByGenericProvider.cs - Pattern matching
• src/LayeredCraft.DecoWeaver.Generators/Providers/DecoratedByNonGenericProvider.cs - Pattern matching
• src/LayeredCraft.DecoWeaver.Generators/AttributeNames.cs - Added metadata name constants
• src/LayeredCraft.DecoWeaver.Generators/Descriptors.cs - Added DECOW020 diagnostic
• test/Cases/022_FactoryDelegate_ShouldNotIntercept/ - New test case
• docs/usage/open-generics.md - Documentation updates

Testing

• All existing tests pass
• New test case verifies factory delegates are not intercepted
• Generated code compiles without errors

🤖 Generated with Claude Code

[ncipollina]

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add missing using for SymbolDisplay

The new Escape helper calls SymbolDisplay.FormatLiteral, but this type lives in the Microsoft.CodeAnalysis namespace, not Microsoft.CodeAnalysis.CSharp. Because the file only imports Microsoft.CodeAnalysis.CSharp, the SymbolDisplay identifier is unresolved and the generator no longer compiles. Import Microsoft.CodeAnalysis (or fully qualify the call) so the project builds.

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