Auto-submit dataset version when exporting workflow results to a dataset

### Feature Summary

When exporting workflow execution results to a dataset, the exported files are uploaded to the dataset's staging area but not committed as a new version. Users must manually navigate to the Datasets tab, select the dataset, and click "Submit" to finalize the export. This adds unnecessary friction to what should be a single-action operation.

### Proposed Solution or Design

After the file upload completes, automatically call the file service's POST /api/dataset/{did}/version/create endpoint to commit the staged files as a new dataset version.

### Impact / Priority

(P2)Medium – useful enhancement

### Affected Area

_No response_