khan: name $cast type

pkg/arvo/sys/lull.hoon

@@ -2106,13 +2106,14 @@
     $%  $>(%born vane-task)                             ::  new unix process
         [%done ~]                                       ::  socket closed
         [%fard p=(fyrd vase)]                           ::  in-arvo thread
-        [%fyrd p=(fyrd (pair mark (cask)))]             ::  external thread
+        [%fyrd p=(fyrd cast)]                           ::  external thread
         $>(%trim vane-task)                             ::  trim state
         $>(%vega vane-task)                             ::  report upgrade
     ==                                                  ::
   ::                                                    ::
   ++  avow  |$  [a]  (each a goof)                      ::  $fyrd result
   +$  bear  $@(desk beak)                               ::  partial $beak
+  +$  cast  (pair mark (cask))                          ::  marked input/output
   ++  fyrd  |$  [a]  [=bear name=term args=a]           ::  external thread
   --  ::khan
 ::

pkg/arvo/tests/sys/vane/khan.hoon

@@ -16,7 +16,7 @@
       call-args=[duct=~[/initial-born-duct] ~ [%born ~]]
     ==
   =/  results-0  (expect-eq !>(~) !>(born-moves))
-  =/  fyrd=(fyrd:khan (pair mark (cask)))  [%base %nonexistent %noun %noun ~]
+  =/  fyrd=(fyrd:khan cast:khan)  [%base %nonexistent %noun %noun ~]
   =/  now=@da  (add ~1111.1.1 ~s1)
   =^  start-moves  khan-gate
     %-  khan-call  :*