Add clustering edge case tests

[fabricekabongo]

Summary

• add tests for cluster state representation and cluster IP resolution error handling
• cover engine decorator broadcast queueing and location broadcast behaviors

Testing

• go test ./...

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Codex Task

[deepsource-io]

Here's the code health analysis summary for commits 7a98498..e08e047. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
Docker	✅ Success		View Check ↗
Secrets	✅ Success		View Check ↗
Test coverage	✅ Success		View Check ↗
Go	✅ Success		View Check ↗

Code Coverage Report

Metric	Aggregate	Go
Composite Coverage	54% (up 5.2% from main)	54% (up 5.2% from main)
Line Coverage	54% (up 5.2% from main)	54% (up 5.2% from main)

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