The floor was an absolute fleet number, so it asserted replicas x per-replica rate
and went red on how many gateway pods happened to be warm rather than on the request
path. The test now measures one replica first, with a short serial pass that only ever
occupies a single pod, and requires the concurrent phase to reach at least that rate.
A serial latency budget carries the request-path assertion the floor used to imply,
and both hold at one replica or seven.
Zero-error runs that "sustained 16.7 RPS" were queueing, not slow requests: the load
model is a mock_response deployment with no upstream, a single-worker replica serves
it in about 57ms, and 100 closed-loop users against 1/0.057 RPS of capacity sit at
6s each by Little's law.
The runner also kept locust's --json summary and threw away everything else, so a run
where 93% of requests failed said nothing about what they got. It now passes --csv,
reads the failure breakdown back, and reports locust's own generator-saturation
warnings, both folded into the assertion messages.
Resolves LIT-5054
