Implement logic session handshake

docs/host_logic_rebuild.md

@@ -47,16 +47,19 @@ Design notes:
 
 ### Node 3: session handshake path
 
-Files planned next:
+Files completed in this step:
 
 - `KeyBorad/KeyBorad/LOGIC/Lgc_Session.h`
 - `KeyBorad/KeyBorad/LOGIC/Lgc_Session.cpp`
 
-Target behavior:
+Implemented behavior:
 
 - try CDC handshake
+- send `HelloReq`
+- wait for `HelloRsp`
 - store the active transport
-- read next parsed packet
+- keep a stream buffer for CDC bytes
+- return the next parsed packet to upper layers
 
 ### Node 4: core facade