Misc signal cleanup

[isaacl]

• Fix test msg

• Remove proc 'exit' handler during interrupt
  This code was a no-op as spawn.js does not emit exit events.
  This is actually good, because were it to be working, it would
  result in a race condition when a child exits non-zero:

  1. The lifecycle promise would be rejected, leading to log output
     and a possible pnpm exit
  2. This hook would force node to exit 0 immediately.

• Fix the listener removals when child exits.