Uses Zuse's previously unused +harden helper function to streamline
+task unwrapping in vanes.
(Arguably, in landlocked vanes like Ford, we should crash if we get a
%soft task, since no events should be coming in directly from the
outside.)
This broke when %kick was handled by resubscribing on your own ship
because it processed the %kick before the %leave. For example, `@t`404
at the dojo would put the dojo in an unworkable state.
You want the %leave to be processed first because you can't do a
"resubscribe" in response to that.
