feat: support abstract intermediate base classes in generator

[ncipollina]

Summary

Adds support for CRTP-style abstract base classes that sit between a concrete enum and OptimizedEnum<TEnum, TValue>. Previously, the abstract base class itself would be processed by the generator and emit a spurious OE0004 (no members found) diagnostic, blocking the pattern entirely.

Changes

src/LayeredCraft.OptimizedEnums.Generator/Providers/EnumSyntaxProvider.cs

• Added if (classSymbol.IsAbstract) return null guard after the FindOptimizedEnumBase check — abstract classes are skipped silently, as they are intermediate base classes rather than concrete enums

tests/.../GeneratorVerifyTests.cs

• AbstractBase_WithCRTP — verifies the CRTP pattern generates exactly one tree (for the concrete subclass) with no spurious diagnostics from the abstract base
• AbstractBase_Alone_ProducesNoOutput — verifies a standalone abstract base produces zero output and zero diagnostics

Directory.Build.props — version bumped 1.1.0 → 1.1.1

Validation

• All 42 tests pass across .NET 8, 9, and 10
• New tests cover both the happy path and the abstract-base-in-isolation case

Release Notes

1.1.1 — Abstract intermediate base classes using the CRTP pattern are now silently skipped by the generator. Concrete subclasses continue to generate correctly with TEnum resolved to the concrete type.

// Now works without spurious OE0004
public abstract partial class DomainEnum<TSelf> : OptimizedEnum<TSelf, int>
    where TSelf : DomainEnum<TSelf>
{
    public string Description { get; }
    protected DomainEnum(int value, string name, string description)
        : base(value, name) { Description = description; }
}

public sealed partial class OrderStatus : DomainEnum<OrderStatus>
{
    public static readonly OrderStatus Pending = new(1, nameof(Pending), "Order is pending");
    private OrderStatus(int value, string name, string description)
        : base(value, name, description) { }
}

🤖 Generated with Claude Code

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Codex Review: Didn't find any major issues. Swish!

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