Type Alias LabelValues

Lightweight metrics registry (spec §15 §14.4).

Prometheus-text-format compatible — apps can scrape /metrics and point Grafana / Datadog / etc. at it. Metric types are intentionally minimal:

• counters (monotonic)
• gauges (set/inc/dec to any value)
• histograms via simple sum + count (we don't ship buckets — those come in v0.5+)

Built dependency-free so we can swap for prom-client later without an API churn.