⚡ Bolt: Remove exception handling overhead in spatial loops

[NoWon1]

💡 What: Removed nested try...except blocks in favor of explicit self.dim.x / self.dim.y boundary checks in CC3D spatial loops.
🎯 Why: Out-of-bounds SWIG object lookups throw exceptions that incur significant overhead in tightly nested spatial loops. Avoiding these via explicit checks drastically speeds up execution.
📊 Impact: Eliminates redundant overhead from exception swallowing per spatial coordinate per simulation step.
🔬 Measurement: Verified functionality by mocking cell_field without dict-based KeyErrors, confirming standard boundaries via test_steppable.py without raising.

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PR created automatically by Jules for task 17066282510680915752 started by @NoWon1

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