🛡️ Sentinel: Fix B607 partial path execution in tests

[ManupaKDU]

🚨 Severity: LOW
💡 Vulnerability: Bandit B607 identified starting a process with a partial path (python3) in tests.
🎯 Impact: Local PATH interception.
🔧 Fix: Used sys.executable for a secure absolute path to the active python interpreter.
✅ Verification: Bandit tests pass and unit tests run cleanly.

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PR created automatically by Jules for task 13767232691444340709 started by @ManupaKDU

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