code: def all
        DirItems.new(path).fetch(recursive: false).select do |f|
          file = File.join(@dir, f)
          basename = File.basename(f, Wallet::EXT)
          File.file?(file) &&
            !File.directory?(file) &&
            basename =~ /^[0-9a-fA-F]{16}$/ &&
            Id.new(basename).to_s == basename
        end.map { |w| Id.new(File.basename(w, Wallet::EXT)) }
      end
docs: Returns the list of their IDs (as plain text)