fix(platform): support Windows storage and native filesystem boundaries

internal/fileutil/space_windows.go

@@ -0,0 +1,14 @@
+package fileutil
+
+import "golang.org/x/sys/windows"
+
+// AvailableBytes returns disk space available to the current user.
+func AvailableBytes(dir string) (uint64, error) {
+	name, err := windows.UTF16PtrFromString(dir)
+	if err != nil {
+		return 0, err
+	}
+	var available uint64
+	err = windows.GetDiskFreeSpaceEx(name, &available, nil, nil)
+	return available, err
+}