test(frontend): extend CoeditorPresenceService coverage

[aglinxinyuan]

What changes were proposed in this PR?

Extends the CoeditorPresenceService spec (was ~19% covered), driving the real yjs Awareness object: join/leave/update handling, yDoc-reload re-registration, shadowing start/stop, cursor pointer branches, incremental highlight diffing, currently-editing tracking, property-changed flash timeout, and code-editor open/close emissions.

Any related issues, documentation, discussions?

Closes #6383.

How was this PR tested?

Extended the spec from 1 to 24 tests against the real WorkflowGraph/SharedModel with spied joint-wrapper coeditor methods. Verified locally with Vitest and CI's format:ci gate clean. Test-only change — no production code is modified.

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 expands the frontend unit test coverage for CoeditorPresenceService by exercising it against a real Yjs Awareness instance and a real WorkflowGraph/SharedModel, verifying collaboration-presence behaviors without changing production code.

Changes:

• Added comprehensive Awareness-driven tests for co-editor add/update/remove, including local-client filtering and stale-removal handling.
• Added coverage for yDoc reload re-observation, shadowing mode behaviors, highlight/currently-editing propagation, and code-editor open/close event emission.
• Added coverage for cursor pointer creation/move/removal and property-changed flash timeout behavior.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.04%. Comparing base (afa8af2) to head (722c1eb).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6386   +/-   ##
=========================================
  Coverage     66.04%   66.04%           
  Complexity     3380     3380           
=========================================
  Files          1142     1142           
  Lines         44980    44980           
  Branches       4948     4948           
=========================================
  Hits          29709    29709           
  Misses        13631    13631           
  Partials       1640     1640           

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from afa8af2
agent-service	51.90% <ø> (ø)		Carriedforward from afa8af2
amber	66.57% <ø> (ø)		Carriedforward from afa8af2
computing-unit-managing-service	9.97% <ø> (ø)		Carriedforward from afa8af2
config-service	52.30% <ø> (ø)		Carriedforward from afa8af2
file-service	63.97% <ø> (ø)		Carriedforward from afa8af2
frontend	63.51% <ø> (ø)		Carriedforward from afa8af2
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from afa8af2
pyamber	91.18% <ø> (ø)		Carriedforward from afa8af2
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from afa8af2

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

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[mengw15]

LGTM