A backend that refuses on a subscription usage limit leaves the pane healthy but
the turn ends with no bridge_reply; the completion fallback used to scrape and
hand that refusal back as if it were a real answer. CompletionResolver now
matches the scrape against a per-profile exhaustedPattern (config, never a
vendor string) and resolves the send as Rendezvous.Kind/Outcome.BACKEND_EXHAUSTED
with a reason carrying the matched line, kept distinct from GONE/WORKER_FAILED.
A profile with no pattern configured is unaffected. Coverage is logged at
startup via CompletionResolver.coverage(...), naming which profiles have a
pattern and which don't, following FleetHealthMonitor.coverage's pattern.
Dai Ha
541df87272