Add longPathForWindows() helper that prefixes extract target directories
with \?\ on Windows, bypassing the 260-char MAX_PATH limit. Applied to
both WinRAR/UnRAR and 7z arguments. Fixes "Die Syntax für den
Dateinamen, Verzeichnisnamen" errors when archive internal directories
create deeply nested output paths.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>