Implement Ax.AcadDocument.__eq__

[CEXT-Dan]

Discussed in #528

^{Originally posted by gswifort June 11, 2026}

>>> Ax.AcadApplication().activeDocument() == Ax.AcadApplication().activeDocument()
False

I can compare fullName, but it's not optimal. Is there another way?

Side question: Is Ax the only way to open a document read-only?