test(frontend): cover updateOrCreatePreset and preset guards

[Ma77Ball]

What changes were proposed in this PR?

• Add branch coverage for PresetService.updateOrCreatePreset (identical, push, no-op, implicit-delete, replace).
• Add tests for the isValidPreset and isValidPresetArray type guards.

Any related issues, documentation, discussions?

Closes: #6690

How was this PR tested?

• Run: cd frontend && node --max-old-space-size=8192 ./node_modules/nx/dist/bin/nx.js test gui --watch=false --include=src/app/workspace/service/preset/preset.service.spec.ts, expect the suite passing.
• Test-only change; no production code is modified.

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

Co-authored with Claude Opus 4.8 in compliance with ASF

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @aglinxinyuan
  You can notify them by mentioning @aglinxinyuan in a comment.

[Copilot]

Pull request overview

This PR adds frontend unit tests to increase coverage for PresetService.updateOrCreatePreset and the Ajv-backed preset type guards, aligning with issue #6690’s goal of improving test coverage in the preset workflow.

Changes:

• Added branch-coverage tests for PresetService.updateOrCreatePreset (identical, append, replacement-exists, implicit-delete, replace).
• Added tests for the isValidPreset and isValidPresetArray Ajv type guards.

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[aglinxinyuan]

Merged main to trigger coverage report.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.27%. Comparing base (110a54c) to head (8b9edb3).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6691   +/-   ##
=========================================
  Coverage     76.27%   76.27%           
  Complexity     3452     3452           
=========================================
  Files          1161     1161           
  Lines         45919    45917    -2     
  Branches       5100     5100           
=========================================
  Hits          35025    35025           
+ Misses         9329     9327    -2     
  Partials       1565     1565           

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from c24755c
agent-service	76.76% <ø> (ø)		Carriedforward from c24755c
amber	67.33% <ø> (ø)		Carriedforward from c24755c
computing-unit-managing-service	20.49% <ø> (ø)		Carriedforward from c24755c
config-service	66.66% <ø> (ø)		Carriedforward from c24755c
file-service	67.21% <ø> (ø)		Carriedforward from c24755c
frontend	81.71% <ø> (+<0.01%)	⬆️	Carriedforward from c24755c
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from c24755c
pyamber	92.15% <ø> (ø)		Carriedforward from c24755c
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from c24755c

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

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[aglinxinyuan]

LGTM!