Clarify sandbox causal edge descriptors

crates/lazaret-runtime-supervisor/src/supervision.rs

@@ -344,7 +344,7 @@ fn runsc_target(arguments: &RuntimeArguments, pid_file: i32) -> io::Result<Targe
     for argument in &arguments.runsc_arguments[run + 1..] {
         target = target.argument(argument);
     }
-    Ok(target)
+    Ok(target.with_parent_death_kill_edge())
 }
 
 fn wait_for_runsc_ready(pid_file: &File, process: &RetainedProcess) -> io::Result<u32> {