test: preserve optional security alternatives

[kriptoburak]

Summary

• Add a regression test for endpointDefinitionRefiner preserving OpenAPI optional security alternatives.
• Cover the apiKey, bearer, and anonymous security requirement shape used by public OpenAPI 3.1 specs.

Validation

• git diff --check
• Not run: pnpm test because this clone has no node_modules and local disk is nearly full.

[vercel]

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