Gate 16 asserts invariants under load: states tracked under concurrent
connections and drained again, 200 ruleset reloads without failure, 2000
table entries flushed back to zero, 2 MB intact through NAT under a
concurrent stream, no kernel faults. Throughput is measured and reported
rather than gated, and the traffic phases run at a bounded rate because
the PF workqueue backlog exhausts a 1 GB guest above ~1 Gbit/s.
The runner writes out/stress/<timestamp>/report.md and captures the guest
serial console so a panic stays diagnosable.
