Request-local latency trace collector.
This is intentionally process-local and opt-in. Normal hot-path calls pay only
the small enabled?/0 check in selected boundaries; traced native requests set
the collector in the lane process and receive the accumulated timings in the
response payload.
Summary
Functions
@spec add(binary(), non_neg_integer()) :: :ok
@spec enabled?() :: boolean()
@spec merge(map()) :: :ok