🧪 Add unit tests for QuadTree.Query(AABB)

[johnstrand]

🎯 What: Missing unit test coverage for QuadTree.Query(AABB) and related QuadTree operations.
📊 Coverage: Added unit tests covering Query(AABB) with empty tree, non-intersecting regions, single/multiple item spatial filtering, subdivided quadtree traversal across child quadrants, multi-quadrant region queries, state changes post-Remove/Clear, radius queries, and bounds validation on Insert.
✨ Result: Comprehensive test suite added for QuadTree.Query(AABB) ensuring spatial queries operate correctly and without regressions.

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PR created automatically by Jules for task 1726573914412587023 started by @johnstrand

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