🧪 Add unit tests for BehaviorTree, Sequence, Selector, and Inverter

[johnstrand]

🎯 What: Add comprehensive unit test coverage for BehaviorTree, Sequence, Selector, and Inverter classes in GameUtils.Entity.BehaviorTree.
📊 Coverage: Covered null argument validation, node evaluation execution order, running state persistence/resumption across ticks, short-circuit evaluation, status inversion, and tree composition.
✨ Result: Ensures complete test coverage and reliability for BehaviorTree module.

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PR created automatically by Jules for task 865033657074058299 started by @johnstrand

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