/**
 * Performance metrics collection via CDP + Playwright page.evaluate().
 *
 * Collects Core Web Vitals and resource timing after page navigation.
 * Stored alongside screen data for test generation context and regression detection.
 *
 * Metrics:
 * - LCP (Largest Contentful Paint) — via PerformanceObserver in page
 * - CLS (Cumulative Layout Shift) — via PerformanceObserver in page
 * - TTFB (Time to First Byte) — from navigation timing
 * - DOMContentLoaded — from navigation timing
 * - Resource count and size by type
 */
export interface CoreWebVitals {
    lcp?: number;
    cls?: number;
    ttfb?: number;
    fcp?: number;
    domContentLoaded?: number;
    loadEventEnd?: number;
}
export interface ResourceSummary {
    scripts: {
        count: number;
        totalBytes: number;
    };
    styles: {
        count: number;
        totalBytes: number;
    };
    images: {
        count: number;
        totalBytes: number;
    };
    fonts: {
        count: number;
        totalBytes: number;
    };
    other: {
        count: number;
        totalBytes: number;
    };
}
export interface PagePerfMetrics {
    url: string;
    vitals: CoreWebVitals;
    resources: ResourceSummary;
    totalTransferBytes: number;
    requestCount: number;
    measuredAt: string;
}
export declare function collectPerfMetrics(page: any, url: string): Promise<PagePerfMetrics>;