Mixed-build lobbies silently corrupt raw-struct replication (night-9: one
stale-zip player, one desynced stream, ghost mechs + K/D doubt). Three
additive edits in btl4lobby.cpp:
1. HOST stamps the lobby with its exact build (btl4ver = BT_VERSION_STRING).
2. JOINER's lobby search filters on build equality -- a stale-zip player
simply finds no lobby, and the "no lobby found" log line NAMES the local
build so the report is self-diagnosing (#68's silent-exit lesson).
3. Post-entry verify (covers invites/direct joins + unstamped older hosts):
mismatch -> log both versions loudly, LeaveLobby, fail the join.
LAN/relay (join.bat) handshake remains a separate 717 item -- this covers
the Steam path the operator asked about.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
