addresses #5442 by adding %thread-done and %thread-fail marks. also
fixes await-thread:strandio and removes some blank lines from
app/spider.hoon
%thread-done loses the type of the result, so you'll need to use ;; to
get it back. the real way to fix this is to have threads produce cages
instead of vases
Kind of a pain to test, need a better way to insert a `charge` directly.
Either that or rework `chad`, but I don't entirely understand why the
`chad` lifecycle is the way it is.
