Makes atmos superconduction a CVar, disables it by default.

Content.Shared/CCVars.cs

@@ -234,6 +234,13 @@ namespace Content.Shared
         public static readonly CVarDef<bool> MonstermosEqualization =
             CVarDef.Create("atmos.monstermos_equalization", true, CVar.SERVERONLY);
 
+        /// <summary>
+        ///     Whether atmos superconduction is enabled.
+        /// </summary>
+        /// <remarks> Disabled by default, superconduction is awful. </remarks>
+        public static readonly CVarDef<bool> Superconduction =
+            CVarDef.Create("atmos.superconduction", false, CVar.SERVERONLY);
+
         /// <summary>
         ///     Maximum time in milliseconds that atmos can take processing.
         /// </summary>