/**
 * Detect whether the Content Credits browser extension is installed.
 *
 * Strategy 1: Load a known icon from the chrome-extension:// URL.
 *   - Fastest and most reliable for Chrome/Edge.
 *
 * Strategy 2: Check a flag the extension sets on window.
 *   - Extension can set `window.__CC_EXTENSION_LOADED = true` in a content script.
 *
 * Strategy 3: Timeout fallback — if neither resolves within DETECTION_TIMEOUT_MS,
 *   assume not installed.
 */
export declare function detectExtension(extensionId: string): Promise<boolean>;