boot: partial prop support

Doesn't yet support pre-userspace props, and the code might need to be
shuffled around a bit, but what's here works already.

pkg/arvo/sys/lull.hoon

@@ -1177,6 +1177,7 @@
         $>(%init vane-task)                             ::  after gall ready
         [%meld ~]                                       ::  unify memory
         [%pack ~]                                       ::  compact memory
+        [%seat =desk]                                   ::  install desk
         [%shot ses=@tas task=session-task]              ::  task for session
         [%talk p=(list tank)]                           ::  print tanks
         [%text p=tape]                                  ::  print tape

pkg/arvo/sys/vane/dill.hoon

@@ -107,6 +107,11 @@
           %pack  (dump kyz)
           %crop  (dump trim+p.kyz)
           %verb  (pass /verb %$ kyz)
+        ::
+            %seat
+          %^  pass  /seat  %g
+          :+  %deal   [our our]
+          [%hood %poke %kiln-install !>([desk.kyz our desk.kyz])]
         ==
       ::
       ++  crud

pkg/base-dev/lib/pill.hoon

@@ -322,4 +322,21 @@
     =/  pro  q:$:tap
     [[%cell p.gun p:$:tap] [.*(pro q.gun) pro]]
   --
+::
+++  events
+  |%
+  +$  prop  [%prop meta tier (list ovum)]
+  +$  meta  term
+  +$  tier  ?(%pre-userspace %post-userspace)
+  ::
+  ++  install
+    |=  [as=desk =beak]
+    ^-  prop
+    :^  %prop  %install  %post-userspace
+    ::TODO  will exclude non-:directories files, such as /changelog/txt
+    :~  (file-ovum as (en-beam beak /))
+      ::
+        [/d/install/[as] [%seat as]]
+    ==
+  --
 --