Add unit tests for PresetWrapperComponent

[Yicong-Huang]

Task Summary

frontend/src/app/common/formly/preset-wrapper/preset-wrapper.component.spec.ts exists but its body is currently a placeholder. Formly field wrapper that integrates operator-property preset persistence into the operator form. The spec body is currently entirely commented out. Add real test cases against the current component/service shape.

Follow-up to the Vitest migration umbrella #4861; placeholder specs were intentionally left out of #4880's scope so #4880 can track real spec migrations and these can be sized individually.

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other