DISK_AVAILABLE disk available space (bytes)
example: stdlib.disk_available('/')
Ref: https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/File.html#getUsableSpace()
function f = disk_available(d) arguments d (1,1) string end f = javaFileObject(d).getUsableSpace(); end %!assert (disk_available('.') > 0)