Expand-Archive was failing with a cryptic "End of Central Directory record
could not be found" on Melissa's PC - the inline one-liner in setup.bat had
no error handling, so a blocked/truncated download (antivirus, firewall, or
an older TLS default) surfaced as a raw .NET exception instead of a useful
message. Moved the logic to Get-WinSCP.ps1: forces TLS 1.2, validates the
downloaded file size before unzipping, and reports what actually went wrong.
