test(frontend): add unit test coverage for DatasetSelectionModalComponent

[mengw15]

What changes were proposed in this PR?

Adds a Vitest spec for DatasetSelectionModalComponent
(frontend/src/app/workspace/component/dataset-selection-modal/), which
previously had no spec (codecov ~11%).

6 tests, using TestBed + detectChanges(), with DatasetService and
NzModalRef stubbed (vi.fn() returning of(...)) and NZ_MODAL_DATA
provided so the modal receives its { fileMode, selectedPath }:

• create + render — loads accessible datasets on init; the confirm button
  renders disabled until a path is chosen.
• ngOnInit from data.selectedPath — in file mode, splits the path into
  owner / dataset / version and initializes selectedDataset, datasetVersions,
  selectedVersion, and fileTree accordingly.
• onDatasetChange — loads the version list and (in file mode) auto-selects
  a version.
• onVersionChange — in non-file mode, composes selectedPath as
  /owner/dataset/version and loads the file tree.
• onFileSelected — in file mode, sets selectedPath to the node's full path.
• onConfirmSelection — closes the modal with selectedPath.

DatasetService is stubbed inline (no shared stub exists for it). No production
code was changed.

Any related issues, documentation, discussions?

Closes #6516

How was this PR tested?

New unit tests, run locally in frontend/ (all green; the failure path was
verified by breaking an assertion to confirm the suite goes red):

ng test --watch=false --include src/app/workspace/component/dataset-selection-modal/dataset-selection-modal.component.spec.ts
# Tests  6 passed (6)
eslint <spec>       # clean
prettier --check    # clean

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Opus 4.8 [1M context])

[github-actions]

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[Copilot]

Pull request overview

Adds Vitest unit test coverage for DatasetSelectionModalComponent (Angular standalone component under frontend/src/app/workspace/component/dataset-selection-modal/) by introducing a new spec file; no production/frontend runtime code is modified.

Changes:

• Added a new DatasetSelectionModalComponent Vitest spec covering initialization, dataset/version/file selection flows, and confirm behavior.
• Stubbed DatasetService and NzModalRef and provided NZ_MODAL_DATA to drive modal behavior in tests.

---

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.99%. Comparing base (39db110) to head (5839ad2).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6529      +/-   ##
============================================
+ Coverage     70.57%   70.99%   +0.41%     
  Complexity     3425     3425              
============================================
  Files          1146     1146              
  Lines         45062    45078      +16     
  Branches       4960     4972      +12     
============================================
+ Hits          31802    32001     +199     
+ Misses        11613    11424     -189     
- Partials       1647     1653       +6     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from 39db110
agent-service	76.76% <ø> (ø)		Carriedforward from 39db110
amber	66.72% <ø> (ø)		Carriedforward from 39db110
computing-unit-managing-service	17.72% <ø> (ø)		Carriedforward from 39db110
config-service	52.30% <ø> (ø)		Carriedforward from 39db110
file-service	66.80% <ø> (ø)		Carriedforward from 39db110
frontend	70.34% <ø> (+0.97%)	⬆️
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from 39db110
pyamber	91.74% <ø> (ø)		Carriedforward from 39db110
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from 39db110

*This pull request uses carry forward flags. Click here to find out more.

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[aglinxinyuan]

LGTM!