🧪 [testing improvement] Add edge cases for StringExtensions.TryGet

[johnstrand]

🎯 What: Added boundary tests for int.MaxValue and int.MinValue indices for StringExtensions.TryGet.
📊 Coverage: Out of bounds scenario covering the max and min integer range is now verified.
✨ Result: Test robustness improved.

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PR created automatically by Jules for task 8613533855408370895 started by @johnstrand

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