🛡️ Sentinel: [CRITICAL] Fix prefix-matching path traversal bypass in Lua sandbox

[mleem97]

🚨 Severity: CRITICAL

💡 Vulnerability:
The Lua sandbox (GregIoLuaModule, LuaModuleLoader, LuaHotReload) relied on String.StartsWith to validate sandboxed file paths. Because the base paths (e.g., /mod/data) did not have a guaranteed trailing directory separator, an attacker could supply a path that begins with the exact string but maps to a different directory (e.g., /mod/data-secret). Since /mod/data-secret starts with /mod/data, the StartsWith check would incorrectly pass, granting the sandbox access to restricted files.

🎯 Impact:
A malicious or compromised Lua script could escape its designated sandbox (data folder or mod directory) to read, modify, or delete sensitive files in adjacent directories that shared the same string prefix, leading to arbitrary file read/write issues.

🔧 Fix:
Updated the validation logic in the Lua layer:

1. GregIoLuaModule.cs: Ensured dataDirFull appends a trailing directory separator before prefix matching, while still permitting an exact path match.
2. LuaModuleLoader.cs: Ensured both the _modRoot and _sharedRoot directories use a trailing separator before calling StartsWith().
3. LuaHotReload.cs: Ensured the _watchRoot directory appends a trailing separator before prefix matching.

✅ Verification:

• Ran the core test projects.
• Compiled the project using dotnet build gregCore.csproj -c Release.
• Verified the learning was appended to the sentinel.md journal.

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PR created automatically by Jules for task 11667858838311463278 started by @mleem97

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