Event_log.WriterAppend-only writer. Not thread-safe — use one writer per file.
val create : string -> tcreate path opens path for writing, creating it if absent or truncating it if present. Writes the 64-byte header.
val append : t -> Event_types.Event.t -> unitAppend one event. Computes bin_prot size, writes length, crc32, then the bin_prot bytes. Updates running record_count, start_time, end_time.
val close : t -> unitFlush OS buffers and rewrite the header with final counts/timestamps.
val record_count : t -> int64