test: cover Xquik queries and fix CLI docs

[kriptoburak]

Summary

• add generator coverage for a real Xquik tweet-search operation
• verify required and optional query parameter types plus fetcher URL generation
• fix the getting-started command to invoke the published @openapi-codegen/cli package
• correct 2 nearby README typos

Independent repository fix

The README previously instructed users to run npx openapi-codegen, but this repository publishes the CLI as @openapi-codegen/cli. The corrected command now matches the initialization command and package name.

Validation

• pnpm test -- --run (242 tests)
• pnpm check
• pnpm build

The branch is rebuilt on current main as 1 signed commit.

[kriptoburak]

I refreshed this PR on current main as one signed commit. In addition to the Xquik generator fixture, it now fixes the README command that referenced the wrong unscoped CLI package and corrects two nearby typos. All 242 tests, repository checks, and builds pass.