⚡ Bolt: [performance improvement]

[ManupaKDU]

💡 What: Replaced the isinstance check with an exact type() check inside the is_reachable function.
🎯 Why: isinstance has overhead due to class inheritance traversal and tuple checks. When operating in a high-frequency loop with pre-instantiated final classes (like ipaddress.IPv4Address), exact type matching acts as a significantly faster fast path.
📊 Impact: Expected ~2x speedup in the type-validation phase of the execution.
🔬 Measurement: Verified by running internal benchmarks comparing isinstance to type() is. Code functionality remains intact (all 19 unit tests pass).

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PR created automatically by Jules for task 5836923645179668436 started by @ManupaKDU

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