Sends notifications via `openclaw system event --text <msg> --mode now`.
- Always logs locally (info/warning/error) regardless of CLI availability
- Gracefully handles FileNotFoundError (openclaw not on PATH) and
TimeoutExpired; notifications are best-effort and never crash the pipeline
- OPENCLAW_SIGNAL_NUMBER env var stored for future direct-signal support
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
