Skipped unless GOADMIN_BENCH_ADDR points at a running server, so `go test
./...` is unaffected.
Reports latency percentiles rather than an average, which is what capacity
planning needs, and a status-code distribution - that last part is how the rate
limiter's 200-on-rejection was found, since throughput alone looked excellent
while nothing reached a handler.
Includes a routing-floor control case. When a business endpoint matches it, the
measurement has stopped describing the endpoint and started describing the
transport, or the load generator when both share a machine.
