🛡️ Sentinel: [CRITICAL] Fix arbitrary code execution via git config in untrusted repositories

[tachyon-beep]

🚨 Severity: CRITICAL
💡 Vulnerability: Python's subprocess.run(["git", ...]) is vulnerable to RCE if an attacker provides a malicious .git/config configuring core.fsmonitor to execute arbitrary shell scripts. Although src/wardline/core/attest.py properly safeguarded this with _SAFE_GIT_CONFIG, other files (delta.py, legis.py) were vulnerable to this when running git against an untrusted repository.
🎯 Impact: Arbitrary code execution when the static analyzer runs on a maliciously crafted untrusted repository.
🔧 Fix: Updated all subprocess.run calls that invoke git across delta.py and legis.py to use _SAFE_GIT_CONFIG = ("-c", "core.fsmonitor=false"), consistent with attest.py.
✅ Verification: Ensure the updated test_delta.py passes successfully, validating that the parameter is properly passed. Also validated via make ci. Included a Sentinel journal entry as required.

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PR created automatically by Jules for task 4268978496008176289 started by @tachyon-beep

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