Improve IPP diagnostics for Epson issue #75

[boingball]

Summary

• bump windows_ipp_probe.py to v2.4
• add --diagnose mode that sends read-only Get-Printer-Attributes requests
• test IPP/1.1, 1.0 and 2.0 against the supplied endpoint and common legacy paths
• preserve HTTP status, Content-Type, Content-Length, Server, Location and a bounded body preview when the reply is not a valid IPP packet
• keep the normal probe behaviour unchanged unless --diagnose is requested

Why

Issue #75 currently reduces the Epson XP-345 response to:

IPP response is shorter than the 8-byte header

That does not distinguish a wrong path, redirect, HTML error page, empty HTTP response, IPP version rejection, or a real malformed IPP reply. This diagnostic output should tell us which one it is before changing MintPRINT's Amiga-side query logic.

Test command for #75

python windows_ipp_probe.py http://PRINTER-IP:631/ipp/print --all --diagnose

Please attach the complete output, including the endpoint/version diagnostics section.