Raise source-generator coverage toward 99%

[JerrettDavis]

Coverage review shows the largest maintained-source gaps are in source generator implementations.

Top uncovered line counts from the source-only local report:

• src/PatternKit.Generators/ProxyGenerator.cs: 65 uncovered lines
• src/PatternKit.Generators/Factories/FactoriesGenerator.cs: 48 uncovered lines
• src/PatternKit.Generators/StateMachineGenerator.cs: 39 uncovered lines
• src/PatternKit.Generators/Adapter/AdapterGenerator.cs: 30 uncovered lines
• src/PatternKit.Generators/FacadeGenerator.cs: 28 uncovered lines
• src/PatternKit.Generators/DecoratorGenerator.cs: 28 uncovered lines
• src/PatternKit.Generators/Factories/AbstractFactoryGenerator.cs: 24 uncovered lines
• src/PatternKit.Generators/ComposerGenerator.cs: 23 uncovered lines

Acceptance criteria:

• Add TinyBDD generator scenarios for missing diagnostics, namespace/type-shape variants, duplicate/invalid inputs, escaping, and emission branches.
• Prioritize generators with the most uncovered lines first.
• Keep full solution coverage above 95%, with progress toward 99%+.

[JerrettDavis]

Starting implementation on the first generator coverage slice. I am going to regenerate maintained-source coverage locally, identify exact uncovered lines, and add focused TinyBDD generator scenarios for the largest gaps first.

[JerrettDavis]

Merged the first generator coverage slice via #417. It adds ProxyGenerator edge-case scenarios and fixes the sync-return + CancellationToken proxy emission bug that produced invalid async return types. PR and main are green, including Codecov project/patch checks. Remaining generator coverage work should continue with FactoriesGenerator, StateMachineGenerator, AdapterGenerator, FacadeGenerator, and DecoratorGenerator.

[JerrettDavis]

Continuing with the next generator coverage slice on a fresh branch. Targeting FactoriesGenerator first, then I will re-measure and pick the next highest remaining generator gap.

[JerrettDavis]

Merged the FactoriesGenerator coverage slice via #418. FactoriesGenerator uncovered lines dropped from 48 to 19 in the generator-only maintained-source report, and main is green. Continuing with StateMachineGenerator next.

[JerrettDavis]

Merged the StateMachineGenerator coverage slice via #419. StateMachineGenerator uncovered lines dropped from 39 to 12 in the generator-only maintained-source report, and main is green across CI, docs, CodeQL, and Codecov. Next coverage targets remain AdapterGenerator, FacadeGenerator, DecoratorGenerator, and AbstractFactoryGenerator.

[JerrettDavis]

Continuing with the next generator coverage slice on AdapterGenerator. Main is currently green; I will target the remaining uncovered adapter emission and diagnostic branches next.

[JerrettDavis]

AdapterGenerator coverage slice is up in #420. Local generator-only coverage now has AdapterGenerator at 99.2% source coverage, up from 95.4%, with focused TinyBDD coverage for invalid map signatures, unbound adaptees, abstract/internal constructors, partial adapter coexistence, ref readonly/default emission, and metadata-only target/conflict paths. I am watching CI now.

[JerrettDavis]

#420 is merged and main is green at 695af52. AdapterGenerator moved from 95.4% to 99.2% in the generator-only source coverage report. Next slice: AbstractFactoryGenerator, currently about 90.4%.

[JerrettDavis]

AbstractFactoryGenerator coverage slice is up in #421. Local generator-only coverage moved AbstractFactoryGenerator from 90.4% to 97.6%, covering char escaping, default products, base-class contract products, blank service-provider method suppression, primitive key compatibility diagnostics, and unsupported double key formatting. Watching CI now.

[JerrettDavis]

#421 is merged. AbstractFactoryGenerator moved from 90.4% to 97.6% in local generator-only source coverage. Main post-merge CI/docs/CodeQL are running for 6cddeb6 now.