Make guidebook start with some entries collapsed (#16181)

Content.Client/UserInterface/Systems/Guidebook/GuidebookUIController.cs

@@ -116,7 +116,7 @@ public sealed class GuidebookUIController : UIController, IOnStateEntered<LobbyS
     }
 
     /// <summary>
-    ///     Opens the guidebook.
+    ///     Opens or closes the guidebook.
     /// </summary>
     /// <param name="guides">What guides should be shown. If not specified, this will instead list all the entries</param>
     /// <param name="rootEntries">A list of guides that should form the base of the table of contents. If not specified,
@@ -162,6 +162,11 @@ public sealed class GuidebookUIController : UIController, IOnStateEntered<LobbyS
         }
 
         _guideWindow.UpdateGuides(guides, rootEntries, forceRoot, selected);
+
+        // Expand up to depth-2.
+        _guideWindow.Tree.SetAllExpanded(false);
+        _guideWindow.Tree.SetAllExpanded(true, 1);
+
         _guideWindow.OpenCenteredRight();
     }