XmlDocument reports no diagnostics for invalid xml

[DoctorKrolic]

Steps to reproduce:

using Microsoft.Language.Xml;

var document = Parser.ParseText("""
    <Test>
        <
    </Test>
    """);

Console.WriteLine(document.ContainsDiagnostics);

Expected output:
True

Actual output:
False

The diagnostic is actually there on a nested node in the debugger, but both ContainsDiagnostics and GetDiagnostics() on parent nodes/document pretend like nothing is actually there

[KirillOsenkov]

good bug!