🛡️ Sentinel: Fix unused insecure code and harden tests against XXE

[google-labs-jules]

🛡️ Sentinel: [CRITICAL/HIGH] Fix unused insecure code and harden tests against XXE

🚨 Severity: MEDIUM (Defense in Depth)
💡 Vulnerability:

1. Unused Code: The write(xmlFile: XMLDocument, directory: URL) method in FileWriter.swift utilized XMLDocument (from FoundationXML on Linux) but was dead code in the production path.
2. Insecure XML Parsing in Tests: Tests were initializing XMLDocument with empty options [], which defaults to allowing external entity loading, posing a theoretical XXE risk if test inputs were malicious.

🎯 Impact:

1. Reduces attack surface by removing unused code that relied on a potentially vulnerable library configuration.
2. Prevents XXE attacks during test execution, ensuring the development environment is secure.

🔧 Fix:

1. Removed the unused write(xmlFile:...) method.
2. Updated test cases to explicitly use .nodeLoadExternalEntitiesNever when parsing XML for validation.

✅ Verification:

• Verified FileWriter.swift no longer contains the insecure method.
• Verified tests explicitly disable external entity loading.
• Confirmed mise.lock is unchanged.

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PR created automatically by Jules for task 8350166742573447553 started by @alexey1312

[google-labs-jules]

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