- add child.on('error') so a detached-daemon spawn failure can't crash the
  OpenCode process asynchronously (outside activate's try/catch)
- only set HUB_OC_PROXY/HUB_PROXY_PORT once a daemon is listening or spawned;
  when proxy.js is missing, stay in-process instead of routing to a dead port
- clear isListening's probe timer; bounded readiness poll after spawn so the
  first request doesn't race the daemon bind