vere: add undocumented -h option

-h starts %khan. We don't want to run the control plane just anywhere,
to discourage Earth leaking into Mars. Using it should feel like you're
taking off the warranty sticker on your Urbit; this seems sufficient.

pkg/urbit/daemon/main.c

@@ -67,6 +67,7 @@ _main_getopt(c3_i argc, c3_c** argv)
   u3_Host.ops_u.dry = c3n;
   u3_Host.ops_u.gab = c3n;
   u3_Host.ops_u.git = c3n;
+  u3_Host.ops_u.hos = c3n;
 
   //  always disable hashboard
   //  XX temporary, remove once hashes are added
@@ -88,7 +89,7 @@ _main_getopt(c3_i argc, c3_c** argv)
   u3_Host.ops_u.kno_w = DefaultKernel;
 
   while ( -1 != (ch_i=getopt(argc, argv,
-                 "X:Y:G:J:B:b:K:A:H:I:C:w:u:e:F:k:n:p:r:i:Z:LljacdgqstvxPDRS")) )
+                 "X:Y:G:J:B:b:K:A:H:I:C:w:u:e:F:k:n:p:r:i:Z:LljacdghqstvxPDRS")) )
   {
     switch ( ch_i ) {
       case 'X': {
@@ -198,6 +199,7 @@ _main_getopt(c3_i argc, c3_c** argv)
       case 'c': { u3_Host.ops_u.nuu = c3y; break; }
       case 'd': { u3_Host.ops_u.dem = c3y; break; }
       case 'g': { u3_Host.ops_u.gab = c3y; break; }
+      case 'h': { u3_Host.ops_u.hos = c3y; break; }
       case 'P': { u3_Host.ops_u.pro = c3y; break; }
       case 'D': { u3_Host.ops_u.dry = c3y; break; }
       case 'q': { u3_Host.ops_u.qui = c3y; break; }

pkg/urbit/include/vere/vere.h

@@ -283,6 +283,7 @@
         c3_c*   gen_c;                      //  -G, czar generator
         c3_o    gab;                        //  -g, test garbage collection
         c3_c*   dns_c;                      //  -H, ames bootstrap domain
+        c3_o    hos;                        //  -h, hosted env (run control plane)
         c3_c*   jin_c;                      //  -I, inject raw event
         c3_c*   imp_c;                      //  -i, import pier state
         c3_c*   lit_c;                      //  -J, ivory (fastboot) kernel

pkg/urbit/vere/io/khan.c

@@ -256,6 +256,10 @@ _khan_io_talk(u3_auto* car_u)
 {
   u3_khan* kan_u = (u3_khan*)car_u;
 
+  if ( c3n == u3_Host.ops_u.hos ) {
+    // do not run control plane outside of hosted context
+    return;
+  }
   u3_noun wir = u3nt(c3__khan,
                      u3dc("scot", c3__uv, kan_u->sev_l),
                      u3_nul);