fix: avoid Expand-Archive dependency on Windows

[anthonystepvoy]

Summary

Fixes #1 by removing the installer's dependency on the Microsoft.PowerShell.Archive module.

Root cause

The remote Windows installer called Expand-Archive. On affected PowerShell installations, command discovery found the module but automatic loading failed, so installation stopped before Caveman files were copied.

Changes

• Extract downloaded ZIP archives through System.IO.Compression.ZipFile.
• Use Invoke-WebRequest -UseBasicParsing for Windows PowerShell 5.1 compatibility.
• Exercise the real remote-download and ZIP-extraction path with a temporary local HTTP server.
• Run that regression test under Windows PowerShell 5.1 in CI.
• Enforce LF endings for shell scripts and workflows across platforms.

Verification

• python scripts/validate-package.py
• Bash syntax and functional installer tests
• PowerShell 7 remote install/uninstall test
• Windows PowerShell 5.1 remote install/uninstall test
• git diff --check