add unit test coverage for DatasetSelectionModalComponent

[mengw15]

Task Summary

frontend/src/app/workspace/component/dataset-selection-modal/dataset-selection-modal.component.ts (codecov ~11%, no spec) — Vitest spec (TestBed + detectChanges()). See frontend/TESTING.md.

Behavior to cover

• should create; detectChanges() renders
• ngOnInit initializes selectedDataset / selectedVersion / selectedPath from the injected data (incl. data.selectedPath)
• dataset / version selection updates the corresponding state
• confirm returns the selected { dataset, version, path }

Task Type

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