fix: accept non-object OpenAPI example values

[Himenon]

Summary

• Add an OpenAPI 3.0 fixture covering non-object values in Parameter, Media Type, Header, and Link objects.
• Generate a Functional API Client from the fixture.
• Add snapshot coverage and validator regression tests.

Specification

OpenAPI Specification v3.0.3 defines example as Any for the Parameter Object and Media Type Object. The Header Object follows the Parameter Object structure, and the Link Object allows Any values for parameters and request bodies.

TDD

This first commit intentionally contains the regression tests and fixture before the validator implementation. The implementation will be added in a follow-up commit.

Fixes #154