Refactor `cmdCheck` in `src/cmd-check.mjs` to support dependency injection for better testability.
Add `test/cmd-check.test.mjs` with comprehensive unit tests for `cmdCheck`, covering happy paths and edge cases.
Verify tests pass with `node --test test/cmd-check.test.mjs`.
Co-authored-by: PR0M3TH3AN <[email protected]>