[Alec Gibson (alecgibson)]

Fixes #165

When Reflect.defineMetadata exists but the registry doesn't, CreateMetadataRegistry wraps the existing Reflect in a fallback provider. The provider captures five methods, and isProviderFor calls getOwnMetadataKeys on every lookup. So if some other library put only part of the API on Reflect, every metadata lookup throws TypeError: getOwnMetadataKeys is not a function.

To reproduce:

1. Install reflect-metadata@0.2.2 and @abraham/reflection, which defines defineMetadata but not getOwnMetadataKeys.
2. Import @abraham/reflection before reflect-metadata.
3. Call Reflect.getOwnMetadata("a", {}). It throws the error above.

With this change, the fallback is only used when all five methods it captures are functions. Otherwise reflect-metadata installs its own implementation, as it does when no metadata API is present. The trade-off is that metadata written through an incomplete implementation before reflect-metadata loads can't be read afterwards, which is better than failing on every lookup.

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

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