SubscribeAsync now wraps each driver handle in a private HostBoundHandle
that carries the resolved host name. UnsubscribeAsync unwraps it and
routes through the recorded host's resilience pipeline, correctly
charging the subscription's originating host's circuit breaker/bulkhead
instead of always using the default host. Falls back to the default
host for handles not created by this invoker. Two regression tests
added; update findings.md Open count from 10 to 6.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ce86deca62