3-way sync proposal

[Alan-Jowett]

This pull request introduces a comprehensive migration plan for transitioning the media streaming protocol from the legacy 5-byte START discovery model to a new, configurable 3-way handshake mechanism (SYN / SYN-ACK / ACK). The migration is designed to be backward compatible, with the new behavior gated behind a runtime flag, ensuring existing deployments are unaffected unless explicitly enabled. The plan details the steps, file locations, implementation guidance, and testing strategies required for a safe and incremental rollout.

The most important changes are:

Protocol and Handshake Implementation:

• Introduces new ProtocolFlag constants (c_udpDatagramFlagSyn, c_udpDatagramFlagSynAck, c_udpDatagramFlagAck) and helper functions (MakeSynTask, MakeSynAckTask, MakeAckTask, ParseControlFrame) to support the new handshake, with implementations in ctsMediaStreamProtocol.hpp and ctsMediaStreamProtocol.cpp.
• Updates send-side logic in ctsIOPatternMediaStream.cpp to optionally send a headered SYN control frame when the 3-way handshake is enabled, while preserving the legacy START behavior by default.
• Modifies receive-side parsing and handshake state management to recognize new control frames, manage handshake state transitions, and maintain compatibility with connection-id datagrams.

**Configuration and Back