/**
 * Append-only NDJSON transition log writer and reader.
 *
 * The transitions.log file stores one JSON record per line (NDJSON format).
 * Each record is a TransitionRecord capturing a phase transition event.
 *
 * Write semantics:
 * - Uses O_WRONLY | O_APPEND | O_CREAT flags for atomic appends.
 * - Concurrent appends from separate processes cannot corrupt existing lines.
 *
 * Read semantics:
 * - File not found → empty array (no error).
 * - Empty lines are skipped.
 * - Malformed JSON lines are skipped with a warning to stderr.
 *
 * Requirements: 4.3, 4.4, 11.5
 */
import type { TransitionRecord } from '../core/types.js';
/**
 * Append a single transition record to the NDJSON log file.
 *
 * Creates the file (and parent directories) if it does not exist.
 * Uses O_APPEND to guarantee atomic line appends even under concurrent writes.
 *
 * @param logPath - Absolute or relative path to the transitions.log file.
 * @param record - The transition record to append.
 */
export declare function appendTransition(logPath: string, record: TransitionRecord): void;
/**
 * Read all transition records from the NDJSON log file.
 *
 * - Returns an empty array if the file does not exist.
 * - Skips empty lines.
 * - Skips malformed JSON lines (logs a warning to stderr).
 *
 * @param logPath - Absolute or relative path to the transitions.log file.
 * @returns Array of parsed TransitionRecord entries.
 */
export declare function readTransitions(logPath: string): TransitionRecord[];
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