Add Xquik OpenAPI parser fixture

[kriptoburak]

Summary

• Add an Xquik OpenAPI 3.1 fixture with account, search, compose, and webhook operations.
• Add parser coverage for generated command names, query parameters, and request body schemas.
• Keep the fixture local so it does not depend on external network calls.

Validation

• pnpm exec vitest run tests/xquik-spec.test.ts
• pnpm build
• pnpm test reaches 153 passed tests, then 3 live Petstore E2E checks fail because pet ID 1 returns 404 from the remote service.
• Link check: https://xquik.com and https://xquik.com/openapi.json returned 200.