test(frontend): extend OperatorMetadataService unit test coverage

[mengw15]

What changes were proposed in this PR?

Extends the existing Vitest spec for OperatorMetadataService
(frontend/src/app/workspace/service/operator-metadata/operator-metadata.service.ts,
codecov ~56%). The service fetches operator metadata once over HTTP (cached via
shareReplay) and serves lookups from it; the existing spec only lightly
touched this. Adds 8 tests using HttpClientTestingModule, each flushing the
metadata GET with the mockOperatorMetaData fixture. No production code changed.

• getOperatorMetadata — emits the fetched metadata to subscribers.
• getOperatorSchema — returns the matching OperatorSchema for a known
  type; throws for an unknown type; throws "operator metadata is undefined"
  before the request resolves.
• operatorTypeExists — true for a fetched type, false for an unknown
  one and before the request resolves; matches the user-friendly name only when
  that filter is enabled; honors case-insensitive matching when requested.

Any related issues, documentation, discussions?

Closes #6592

How was this PR tested?

Extended 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/service/operator-metadata/operator-metadata.service.spec.ts
# Tests  11 passed (11)   (3 existing + 8 new)
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]

Automated Reviewer Suggestions

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

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

[Copilot]

Pull request overview

This PR extends the frontend unit test coverage for OperatorMetadataService by adding more thorough Vitest cases around metadata fetching/caching and schema/type lookup behaviors. It strengthens confidence in the service’s observable caching and error/edge-case handling without changing production code.

Changes:

• Added a shared flushMetadata helper to consistently flush the constructor-triggered metadata GET request with mockOperatorMetaData.
• Added unit tests covering getOperatorMetadata, getOperatorSchema (success + error cases), and operatorTypeExists (pre-fetch, user-friendly-name filter, and case-insensitive matching).

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.01%. Comparing base (c543d77) to head (5063041).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6602      +/-   ##
============================================
+ Coverage     73.98%   74.01%   +0.03%     
  Complexity     3434     3434              
============================================
  Files          1157     1157              
  Lines         45621    45621              
  Branches       5031     5031              
============================================
+ Hits          33752    33766      +14     
+ Misses        10187    10175      -12     
+ Partials       1682     1680       -2     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from c543d77
agent-service	76.76% <ø> (ø)		Carriedforward from c543d77
amber	66.78% <ø> (ø)		Carriedforward from c543d77
computing-unit-managing-service	17.72% <ø> (ø)		Carriedforward from c543d77
config-service	66.66% <ø> (ø)		Carriedforward from c543d77
file-service	66.80% <ø> (ø)		Carriedforward from c543d77
frontend	77.18% <ø> (+0.07%)	⬆️
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from c543d77
pyamber	91.79% <ø> (ø)		Carriedforward from c543d77
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from c543d77

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

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[aglinxinyuan]

LGTM!