///|
/// Appends a Bytes payload to the file at path for WASM target (fallback to read-merge-write).
pub fn append_bytes_to_file(
  path : String,
  content : Bytes,
) -> Unit raise MoonKVError {
  try {
    if @fs.path_exists(path) {
      let existing = @fs.read_file_to_bytes(path)
      let combined = merge_bytes(existing, content)
      @fs.write_bytes_to_file(path, combined)
    } else {
      @fs.write_bytes_to_file(path, content)
    }
  } catch {
    _ => raise MoonKVError::IOError("Failed to append bytes to file \{path}")
  }
}