export declare class MalformedConfigError extends Error {
    constructor(msg: string);
}
export declare class IncompatibleConfigError extends Error {
    constructor(msg: string);
}
export type SafeAppendStatus = "created" | "appended" | "already-present";
export interface SafeAppendResult {
    status: SafeAppendStatus;
    /** Path of the backup written before mutation. Undefined for status="created"
     *  and status="already-present" (no mutation occurred). */
    backupPath?: string;
}
/**
 * Append `value` to the YAML block-sequence under top-level `key` in `filePath`.
 * Idempotent; backs up the original before any mutation; throws on malformed
 * input or incompatible shape (file is never touched on error).
 */
export declare function safeAppendYamlList(filePath: string, key: string, value: string): SafeAppendResult;