leer: fix jet mismatch

[pkova]

With old jet:

> `(list @tas)`(to-wain:format 'hello\0a\0a')
~[%hello %$]

>`(list @tas)`(to-wain:format 'hello\0a')
~[%hello]

Without old jet:

> `(list @tas)`(to-wain:format 'hello\0a\0a')
~[%hello %$ %$]

>`(list @tas)`(to-wain:format 'hello\0a')
~[%hello %$]

The unjetted behavior certainly seems more reasonable to me so this PR fixes the jet to match the hoon. Here's a generator to test stuff out with:

=>
|%
  ++  to-wain                                           ::  cord to line list
    ::  ~%  %leer  ..part  ~
    |=  txt=cord
    ^-  wain
    =/  len=@  (met 3 txt)
    =/  cut  =+(cut -(a 3, c 1, d txt))
    =/  sub  sub
    =|  [i=@ out=wain]
    |-  ^+  out
    =+  |-  ^-  j=@
        ?:  ?|  =(i len)
                =(10 (cut(b i)))
            ==
          i
        $(i +(i))
    =.  out  :_  out
      (cut(b i, c (sub j i)))
    ~&  `(list @tas)`out
    ?:  =(j len)
      (flop out)
    $(i +(j))
--
:-  %say
|=  [^ [arg=@t ~] ~]
:-  %noun
(to-wain arg)

[ashelkovnykov]

Seems reasonable to me

[joemfb]

Releasing this is blocked on #459. There's also a failure in the fake-ship tests, not sure what the issue is.

[joemfb]

There's a second mismatch here:

> `*`=+(to-wain:format .*(-(+6 '') -<))
[0 0]
> `*`(to-wain:format '')
0

[pkova]

After discussion with @joemfb we decided on the following.

Two reasonable ways of handling unix file -> (list @t) conversions are:

1. Be strict with requiring that the files end in newlines. This is what lune:unix:userlib already does.
2. Be loose and silently normalize, losing invertibility but allowing people to |commit files that have been generated with arbitrarily broken tools.

Strategy number 2 is currently in use. We should probably use strategy 1 for at least some marks, but that involves changing the marks and possibly lune:unix:userlib, not to-wain/%leer.

I made urbit/urbit#6707 to fix the jet mismatch that Joe found, closing this PR for the reasons above.