Major refactor: all SignalR responses now use a single unified `SignalResponseDataMessage` type with binary payloads. JSON responses are Brotli-compressed for efficiency. Removed legacy JSON/Binary response types and MessagePack server-to-client serialization. Updated all serialization extensions for zero-allocation binary ops. Refactored client/server/data source/test code to use new message and serialization model. Improved deserialization robustness for primitives. Modernized and streamlined test suite.
