/**
 * Preference Store Interface.
 *
 * Defines a key-value store for user preferences.
 * Fast lookups by key, permanent lifecycle, separate from the knowledge graph.
 *
 * Part of Phase 5D: Preference Key-Value Store.
 */
/**
 * A stored preference entry.
 */
export interface IPreference {
    readonly key: string;
    readonly value: string;
    readonly updatedAt: string;
}
/**
 * Preference store contract.
 * Simple key-value semantics with list/has helpers.
 */
export interface IPreferenceStore {
    /**
     * Get a preference value by key.
     * @returns The stored value, or null if not found.
     */
    get(key: string): Promise<string | null>;
    /**
     * Set a preference value.
     * Creates the key if it doesn't exist, overwrites if it does.
     */
    set(key: string, value: string): Promise<void>;
    /**
     * Delete a preference by key.
     * @returns true if the key existed and was deleted, false otherwise.
     */
    delete(key: string): Promise<boolean>;
    /**
     * List all stored preferences.
     */
    list(): Promise<readonly IPreference[]>;
    /**
     * Check whether a key exists.
     */
    has(key: string): Promise<boolean>;
}
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