Feature/streams

[pro100andrey]

• BREAKING CHANGES:

  • Stream API: rewritten architecture — StreamBinaryReader now implements TransactionalReader<List<int>> with delegation to state
  • NotEnoughDataException: message changed from required $required bytes to required $required

• New Features:

  • Strings: added writeStringFixed and readStringFixed for fixed-width length-prefixed strings.
  • Stream API: added TransactionalReader<TChunk> interface for abstracting transactional read model
  • Stream API: added ChunkedTransactionalState<TChunk> base class for managing chunk queue and bookmarks
  • Stream API: added TransactionalStreamTransformer<TMessage, TChunk, TReader> — generic StreamTransformer for parsing streams
  • Stream API: BinaryStreamTransformer now extends TransactionalStreamTransformer
  • BinaryWriter: improved writeVarString documentation with examples
  • BinaryReader: peekByte() added bounds check — throws RangeError
  • Examples: full restructuring — removed example/main.dart, added example/basic/, example/network_streaming/, example/file_streaming/