- Fixed type mismatch in disk space calculation (int64 casting)
- Created platform-specific disk space implementations:
* diskspace_unix.go (Linux, macOS, FreeBSD)
* diskspace_windows.go (Windows)
* diskspace_bsd.go (OpenBSD)
* diskspace_netbsd.go (NetBSD fallback)
- All 10 platforms now compile successfully:
✅ Linux (amd64, arm64, armv7)
✅ macOS (Intel, Apple Silicon)
✅ Windows (amd64, arm64)
✅ FreeBSD, OpenBSD, NetBSD
