/**
 * Minimal performance metrics helpers.
 *
 * Only the four utilities that have active runtime callers are kept:
 * `startMetrics`, `endMetrics`, `calculateMemoryDelta`, `formatMemoryUsage`.
 * Everything else (trackPerformance decorator, measureTime, threshold
 * checks, PerformanceMonitor class, global singleton, takePerformanceSnapshot)
 * has been deleted — none of it had a runtime caller. If we ever need
 * richer performance tracking, reach for an external library rather than
 * rebuilding the old subsystem.
 */
import type { PerformanceMetrics } from './types.js';
/**
 * Start a performance measurement. Pair with `endMetrics` to compute a
 * duration + memory delta for a block of work.
 */
export declare function startMetrics(): PerformanceMetrics;
/**
 * End a performance measurement previously started with `startMetrics`.
 */
export declare function endMetrics(metrics: PerformanceMetrics): PerformanceMetrics & {
    duration: number;
};
/**
 * Compute the delta between two memory snapshots.
 */
export declare function calculateMemoryDelta(initial: NodeJS.MemoryUsage, final: NodeJS.MemoryUsage): Record<string, number>;
/**
 * Format a memory usage snapshot into human-readable strings suitable for
 * structured log fields.
 */
export declare function formatMemoryUsage(memory: NodeJS.MemoryUsage): Record<string, string>;
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