🛡️ Sentinel: Migrate to structured clean steps to prevent shell injection

[acebytes]

💡 What: Refactored CacheCategory and CacheCleaner to use structured cleanSteps instead of shell commands.

🎯 Why: Defense-in-depth practice to execute directly via Process and avoid shell expansion vulnerabilities.

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PR created automatically by Jules for task 8891770302228101971 started by @acebytes

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