LMDeploy backend-config info metric

InternLM/lmdeploy main, PrometheusStatLogger in lmdeploy/metrics/loggers.py, read 2026-10-04. On by default and requires NO flag: the endpoint is simply available at the API server port (23333 by default). Label keys are model_name and engine on every metric, where engine carries the dp_rank. Bucket construction reuses vLLM's build_buckets / build_1_2_5_buckets idiom. prometheus_client.Info, set once at construction. TYPE CORRECTED 2026-10-05: prometheus_client Info() is not one of the six metric_type values in schemas/metric_exposure.schema.json (counter/gauge/histogram/summary/log-only/unknown), so 'unknown' is the honest value rather than a near-synonym. The record's own notes already stated the constructor is prometheus_client.Info; the metric_type field now agrees with them.