refactor(frontend): make redundant operator border repaints a no-op

[PG1204]

What changes were proposed in this PR?

When an operator is added, its border was painted by two paths - the operator-add restore and the validation pass, producing the same color. Harmless, but a redundant repaint.

This PR adds a guarded border setter (paintOperatorBorder) in JointUIService that writes rect.body/stroke only when the color actually changes. Both changeOperatorColor and changeOperatorState route their border write through it, so a repaint with the color the border already has becomes a no-op, effectively "painted once" - including on the navigation-return (reload) path.

Deviation from the approach suggested on the issue: the issue suggested dropping the applyOperatorBorder call from the operator-add handler and letting the validation pass set the border. I kept that call and used the guard instead, because changeOperatorStatistics already paints the border via changeOperatorState without checking validity. Dropping applyOperatorBorder would make an invalid operator with a cached "completed" status rely on the validation pass firing afterward to correct green→red, reintroducing the order-dependent border fragility that #5146 removed (and it would break in the edge case where setDynamicSchema skips its emit because the schema is unchanged). The guard reaches the same no-redundant-repaint goal while keeping the border validity-correct regardless of event timing.

Any related issues, documentation, discussions?

Closes #5726

How was this PR tested?

Unit tests:

• JointUIService: the guarded setter skips the write when the border is already the requested color, and writes when it differs.
• WorkflowEditorComponent: added a navigation-return test for a cached Running operator (orange), alongside the existing completed (green), default (gray), invalid (red), and invalid-over-cached-priority cases.
• Full frontend suite: 3739 passing.

Manual (navigated away from a running workflow and back), border restored correctly for:

• Completed operators → green
• Running operators → orange
• Invalid operators → red
• Valid, not run → default gray

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

This PR was co-authored using Claude Code (Anthropic Claude Opus 4.7) 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: @mengw15, @Ma77Ball, @Yicong-Huang
  You can notify them by mentioning @mengw15, @Ma77Ball, @Yicong-Huang in a comment.

[PG1204]

/request-review @Xiao-zhen-Liu

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.95%. Comparing base (49f9e2c) to head (5cb206a).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6927   +/-   ##
=========================================
  Coverage     78.95%   78.95%           
  Complexity     3795     3795           
=========================================
  Files          1161     1161           
  Lines         46084    46087    +3     
  Branches       5110     5111    +1     
=========================================
+ Hits          36384    36387    +3     
  Misses         8077     8077           
  Partials       1623     1623           

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from 49f9e2c
agent-service	76.76% <ø> (ø)		Carriedforward from 49f9e2c
amber	72.20% <ø> (ø)		Carriedforward from 49f9e2c
computing-unit-managing-service	20.49% <ø> (ø)		Carriedforward from 49f9e2c
config-service	66.66% <ø> (ø)		Carriedforward from 49f9e2c
file-service	67.21% <ø> (ø)		Carriedforward from 49f9e2c
frontend	82.91% <100.00%> (+<0.01%)	⬆️
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from 49f9e2c
pyamber	95.38% <ø> (ø)		Carriedforward from 49f9e2c
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from 49f9e2c

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

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