/**
 * Decay Engine — 时效性衰减 (FR-E06)
 *
 * Applies confidence decay to entries that haven't been updated or used:
 * - >90 days without update AND usage_count=0 → confidence *= 0.9
 * - >180 days without update → confidence *= 0.8
 * - confidence < 0.5 after decay → status = 'stale'
 */
import type Database from 'better-sqlite3';
export interface DecayReport {
    decayed: number;
    stalemarked: number;
}
/**
 * Apply time-based confidence decay to knowledge entries.
 *
 * Rules:
 * - >90 days since updated_at AND usage_count=0 → confidence *= 0.9
 * - >180 days since updated_at (regardless of usage) → confidence *= 0.8
 * - After decay, if confidence < 0.5 → status = 'stale'
 *
 * Decay is applied once per governance run (not cumulative within a single run).
 */
export declare function applyDecay(db: Database.Database): DecayReport;
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