Harden the mod against hostile servers and players

- PacketReader for all network data: lengths are checked against the real data
  (Mono allocated the claimed size first - a fake 2 GB length crashed the game)
- FsmSync: remote players can no longer switch arbitrary FSMs - never PLAYER /
  Systems / MSCO objects, CLICK only on FSMs that wait for a click, bolt/assembly
  events only along a transition the FSM really has for that event
- Time/weather (msco.world) and '* ' system-style chat only from the host in P2P
  (the dedicated server filters them itself); other msco.* ids are reserved

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

WorldAdmin.cs

@@ -204,7 +204,7 @@ namespace MSCO
         public static void Receive(byte[] data)
         {
             if (!MenuHelper.InGame || data == null || data.Length < 17) return;
-            using (var r = new BinaryReader(new MemoryStream(data)))
+            using (var r = new PacketReader(data))
             {
                 byte kind = r.ReadByte();
                 int value = r.ReadInt32();