/**
 * File logger for the MCP server.
 *
 * - Default path: ~/.config/b402-solana/logs/mcp-YYYYMMDD.log
 * - Date-stamped filename gives natural daily rotation.
 * - Async append; no blocking on stdout/stderr (which is the MCP transport).
 * - Auto-cleanup: deletes logs older than 7 days on boot.
 * - Override path with B402_LOG_FILE; set to '' to disable.
 *
 * What gets logged:
 *   - Boot: cluster, relayer URL, wallet pubkey
 *   - Tool calls: name, duration_ms, ok|err, error message on failure
 *   - NOT logged: keypair paths, recipient addresses, raw mint addresses,
 *     ciphertext, signatures (signatures are public, but we treat the
 *     correlation between signature + tool call as private metadata).
 */
export interface Logger {
    info(event: string, data?: Record<string, unknown>): void;
    warn(event: string, data?: Record<string, unknown>): void;
    error(event: string, data?: Record<string, unknown>): void;
    close(): void;
}
export declare function createLogger(): Logger;
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