Module metrics 

指标收集模块，提供可插拔的性能监控和统计功能

Metrics collection module providing pluggable performance monitoring and statistics.

This module defines the Metrics trait for collecting performance data, usage statistics, and error rates from AI provider interactions.

Simple, injectable metrics trait used by adapters/clients. Keep the surface minimal: counters, gauges and a timer RAII helper.

Modules

keys

Centralized metric key helpers to standardize naming across adapters

Structs

NoopMetrics

No-op metrics implementation suitable as a default.

NoopTimer

A no-op timer (returned when StartTimer implementations want to return a concrete value).

Traits

Metrics

MetricsExt

Convenience methods for common metric patterns

Timer

Timer interface returned by Metrics::start_timer.