Mod 2.8.1: separate mod version from network protocol version

ModVersion (2.8.1, shown in MSCLoader/MSC Launcher) and ProtocolVersion
(2.8) are separate; only the first two digits are compared (P2P host, Steam
lobby, server info, server browser) and only the protocol version is sent,
so minor updates stay compatible with 2.8 servers, hosts and players.
README: how to publish minor and major updates.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

SteamLobby.cs

@@ -164,7 +164,7 @@ namespace MSCO
                 return;
             }
             LobbyId = new CSteamID(result.m_ulSteamIDLobby);
-            SteamMatchmaking.SetLobbyData(LobbyId, VersionKey, MSCO.ModVersion);
+            SteamMatchmaking.SetLobbyData(LobbyId, VersionKey, MSCO.ProtocolVersion); // ältere Mods vergleichen genau
             if (Created != null) Created(LobbyId);
         }
 
@@ -178,7 +178,7 @@ namespace MSCO
             LobbyId = new CSteamID(result.m_ulSteamIDLobby);
 
             string hostVersion = SteamMatchmaking.GetLobbyData(LobbyId, VersionKey);
-            if (!string.IsNullOrEmpty(hostVersion) && hostVersion != MSCO.ModVersion)
+            if (!string.IsNullOrEmpty(hostVersion) && !MSCO.Compatible(hostVersion))
             {
                 Leave();
                 Fail("Version mismatch (host " + hostVersion + ", you " + MSCO.ModVersion + ")");