Upgrade OpenMcdf to v3.1.4

[Copilot]

OpenMcdf 2.4.1 carries a known moderate-severity vulnerability (NU1902). Upgrading to 3.1.4, which also ships an idiomatic rewritten API.

Package version

• Directory.Packages.props: OpenMcdf 2.4.1 → 3.1.4

API migration (SavedGame.cs)

v3 replaces CompoundFile/CFStream.GetData() with RootStorage and standard Stream semantics:

// Before (v2)
var cf = new CompoundFile(file);
GUIName = Encoding.Unicode.GetString(cf.RootStorage.GetStream("Scenario Description").GetData()).TrimEnd(['\0']);
try { CustomMissionID = BinaryPrimitives.ReadInt32LittleEndian(cf.RootStorage.GetStream("CustomMissionID").GetData()); }
catch (CFItemNotFound) { CustomMissionID = 0; }

// After (v3)
using RootStorage root = RootStorage.Open(file);
using (CfbStream s = root.OpenStream("Scenario Description"))
{
    byte[] data = new byte[s.Length];
    s.ReadExactly(data);
    GUIName = Encoding.Unicode.GetString(data).TrimEnd(['\0']);
}
if (root.TryOpenStream("CustomMissionID", out CfbStream? ms))
{
    using (ms) { byte[] d = new byte[ms.Length]; ms.ReadExactly(d); CustomMissionID = BinaryPrimitives.ReadInt32LittleEndian(d); }
}
else { CustomMissionID = 0; }

Key changes:

• new CompoundFile(stream) → RootStorage.Open(stream)
• CFStream.GetData() → allocate buffer, CfbStream.ReadExactly()
• catch (CFItemNotFound) control-flow → TryOpenStream (no exception for the optional CustomMissionID stream)