Removes the PROTOCOL_VERSION lockstep handshake across the bridge
transports. HandshakeMessage is now an empty marker indicating the
server is ready; the client sends StartupMessage next. Field-presence
and roundtrip behavioral tests are retained — tautological
version-literal assertions were deleted in Sprint 36.
After this lands, genuine schema drift surfaces as MessagePack
missing-field errors downstream, which is the intended signal per
D-192. Client ticket #875 is blocked by this commit and will ride
the same wave; server schema changes in #878 (character_archetype
removal) also depend on PROTOCOL_VERSION already being gone.
types.rs changes are bundled with the broader #877/#878 dead-code
sweep in the following commit, since they share the same file.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.6
c640563fc0