Add source generator for aggregate services (closes #13)

[tillig]

Implements build-time aggregate service generation (#13). A C# source generator emits concrete backing implementations for aggregate service interfaces, replacing the Castle DynamicProxy at runtime for the common case while keeping the proxy as a fallback. This makes aggregate services trimming/NativeAOT safe and significantly faster, with no usage changes — consumers update the package reference and recompile.

How it works

The generator ships inside the existing package under analyzers/dotnet/cs/, so there's nothing extra to reference. It runs in the consumer's compilation, scans for the existing registration/creation call sites (RegisterAggregateService<T>() / (typeof), AggregateServiceGenerator.CreateInstance<T> / (typeof)), and for each statically-visible interface emits:

• a backing class implementing the interface (eager property resolution, TypedParameter forwarding for methods, throwing setters/void methods — mirroring ResolvingInterceptor exactly), and
• a [ModuleInitializer] that registers a factory with a new GeneratedAggregateServiceRegistry.

At runtime CreateInstance consults the registry first and falls back to Castle DynamicProxy when the generator couldn't see the interface statically (runtime-computed Type, generic pass-through helpers, etc.). The generated path also fixes the >16-parameter generic method limitation (#11).

AOT/trimming

• Runtime library is marked IsAotCompatible (net7.0+); the closed-aggregate generated path is genuinely trim/AOT-clean.
• The Castle fallback, open-generic construction, and ref/out methods are individually annotated [RequiresUnreferencedCode]/[RequiresDynamicCode] so warnings surface at the consumer's call site only when those scenarios are used.
• An AGSVC001 info diagnostic flags interfaces that fall back to the proxy.
• Requires Autofac 9.3.0+ (first release with the matching AOT annotations).
• A NativeAOT smoke-test app validates the generated path compiles warning-clean and runs correctly (verified end-to-end with a published native binary).

Scope / known limitations

• Open generic aggregates and ref/out parameter methods are JIT-only (not AOT-safe) and use the dynamic proxy fallback.
• Documentation (readthedocs) is intentionally deferred to a follow-up.

Tests

• Autofac.Extras.AggregateService.Test — 57 runtime tests (behavior parity, fallback, parameter modifiers, constraints, lifetime scopes).
• Autofac.Extras.AggregateService.SourceGenerator.Test — 23 generator snapshot + behavior tests (Verify-based).
• bench/ — BenchmarkDotNet comparison (generated vs proxy: ~2× faster, ~half the allocations).
• AotSmokeTest — NativeAOT publish + execution gate.

[codecov]

Codecov Report

❌ Patch coverage is 95.29617% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.88%. Comparing base (8899832) to head (6d27583).

Files with missing lines	Patch %	Lines
...SourceGenerator/AggregateServiceSourceGenerator.cs	89.33%	3 Missing and 5 partials ⚠️
...AggregateService.SourceGenerator/EquatableArray.cs	80.76%	1 Missing and 4 partials ⚠️
...ggregateService.SourceGenerator/DiscoveryResult.cs	66.66%	0 Missing and 4 partials ⚠️
...s.AggregateService.SourceGenerator/LocationInfo.cs	76.92%	1 Missing and 2 partials ⚠️
...s.AggregateService.SourceGenerator/ModelBuilder.cs	98.47%	0 Missing and 2 partials ⚠️
...teService.SourceGenerator/AggregateServiceModel.cs	94.44%	0 Missing and 1 partial ⚠️
...Extras.AggregateService.SourceGenerator/Emitter.cs	99.54%	0 Missing and 1 partial ⚠️
...as.AggregateService.SourceGenerator/MemberModel.cs	94.44%	0 Missing and 1 partial ⚠️
...AggregateService.SourceGenerator/ParameterModel.cs	87.50%	0 Missing and 1 partial ⚠️
...egateService.SourceGenerator/TypeParameterModel.cs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #24      +/-   ##
===========================================
+ Coverage    94.54%   95.88%   +1.33%     
===========================================
  Files            4       16      +12     
  Lines          110      680     +570     
  Branches        20      127     +107     
===========================================
+ Hits           104      652     +548     
- Misses           1        5       +4     
- Partials         5       23      +18     

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