test: add Xquik OpenAPI 3.1 fixture and repair docs

[kriptoburak]

Summary

• add a compact Xquik OpenAPI 3.1 validation fixture
• cover tweet search response references and API key header security
• match the current paginated tweet and author response structure
• repair 6 removed API documentation routes with maintained repository docs

Independent Repository Fix

The README linked 6 API documentation references to removed website routes that return 404. All 6 now resolve to maintained documentation files and anchors in this repository, addressing #281.

Validation

• focused Xquik Mocha test passed
• quick Node suite passed 109 tests
• TypeScript definition test passed
• ESLint passed
• Prettier passed
• all repaired documentation files and anchors exist
• git diff --check passed

Xquik is an independent third-party service. Not affiliated with X Corp. "Twitter" and "X" are trademarks of X Corp.