A daemon-forced bridge is pinned for as long as the agent runs #1575

Once the forced A2R bridge is up, domain_bridge subscribes in from_domain, so has_external_ros2_subscriber is true and the ordinary on-demand check would keep the bridge alive on its own — the force has done its job. The agent has no feedback from the manager, though, so it re-declares the request every tick, is_daemon_forced stays true forever, and check_and_remove_pubsub_bridges can never remove the bridge even when nothing consumes it. Dropping the pin once a bridge has been observed as demanded would restore the normal lifecycle without a protocol change, and re-bootstrap after a domain_bridge restart still works because the agent keeps sending.