Documents more ConstructionSystem methods. (#7246)

Content.Server/Construction/ConstructionSystem.Guided.cs

@@ -102,6 +102,14 @@ namespace Content.Server.Construction
         }
 
 
+        /// <summary>
+        ///     Returns a <see cref="ConstructionGuide"/> for a given <see cref="ConstructionPrototype"/>,
+        ///     generating and caching it as needed.
+        /// </summary>
+        /// <param name="construction">The construction prototype to generate the guide for. We must be able to pathfind
+        ///                            from its starting node to its ending node to be able to generate a guide for it.</param>
+        /// <returns>The guide for the given construction, or null if we can't pathfind from the start node to the
+        ///          end node on that construction.</returns>
         private ConstructionGuide? GetGuide(ConstructionPrototype construction)
         {
             // NOTE: This method might be allocate a fair bit, but do not worry!