🛡️ Sentinel: Fix syntax error and uninitialized memory risk in PersistenceLayer

[ightevenmckane187]

Fixed a syntax error in crypto.createHmac and mitigated potential uninitialized heap memory leakage hazards in src/os/persistence/PersistenceLayer.ts by replacing Buffer.allocUnsafe with Buffer.alloc. Cleaned up redundant buffer allocations and verified functionality through unit and integration tests.

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PR created automatically by Jules for task 10416942146139292735 started by @ightevenmckane187

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