add ability to restore from snapshot on-demand

mar/snap.hoon

@@ -0,0 +1,16 @@
+::
+::::  /hoon/snap/mar
+  ::
+=,  mimes:html
+|_  snap/snapshot:jael
+++  grow
+  |%
+  ++  mime  [/application/octet-stream (jam snap)]
+  --
+++  grab
+  |%
+  ++  noun  snapshot:jael
+  ++  mime  |=([p=mite:eyre q=octs:eyre] (cue q.q))
+  --
+++  grad  %mime
+--

sys/vane/gall.hoon

@@ -1281,6 +1281,7 @@
         $perm  `%c
         $rule  `%e
         $serv  `%e
+        $snap  `%j
         $them  `%e
         $wait  `%b
         $want  `%a

sys/vane/jael.hoon

@@ -848,6 +848,11 @@
       %+  cure  hen
       [[%meet ship.tac life.tac pass.tac]~ urb]
     ::
+    ::  restore snapshot
+    ::    [%snap snap=snapshot kick=?]
+        %snap
+      (restore-snap hen snap.tac kick.tac)
+    ::
     ::  XX should be a subscription
     ::  XX reconcile with .dns.eth
     ::  request domains

sys/zuse.hoon

@@ -1856,6 +1856,7 @@
           [%nuke ~]                                     ::  cancel tracker from
           [%pubs =ship]                                 ::  view public keys
           [%meet =ship =life =pass]                     ::  met after breach
+          [%snap snap=snapshot kick=?]                  ::  load snapshot
           [%turf ~]                                     ::  view domains
           [%vein ~]                                     ::  view signing keys
           [%vent ~]                                     ::  view ethereum events