test: add Xquik OpenAPI 3.1 parser fixture

[kriptoburak]

Summary

• Add an OpenAPI 3.1 YAML fixture for Xquik's search endpoint.
• Cover parser behavior for server URLs, query parameters, API key security, and resolved response schemas.

Testing

• Ran tests/test_parser.py with Python 3.11.
• Ran Ruff on tests/test_parser.py.

[kriptoburak]

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