- Fan out all targets for an event in parallel goroutines (fire-and-forget)
- Add per-target circuit breaker for retry targets (closed/open/half-open)
- Circuit breaker trips after 5 consecutive failures, 30s cooldown
- Open circuit skips delivery and reschedules after cooldown
- Half-open allows one probe delivery to test recovery
- HTTP/database/log targets unaffected (no circuit breaker)
- Recovery path also fans out in parallel
- Update README with parallel delivery and circuit breaker docs
