refactor(character): replace direct child manipulation with RitsuGodotTreeCompat methods

- Updated NFakeMerchantProceduralCharacterInstantiationPatch and NMerchantRoomProceduralCharacterInstantiationPatch to use RitsuGodotTreeCompat for adding and moving child nodes, ensuring compatibility across game versions.
- Introduced RitsuGodotTreeCompat class to provide safe methods for tree mutations, addressing issues with multi-version builds.

Author: BAKAOLC

Scaffolding/Characters/Patches/NFakeMerchantProceduralCharacterInstantiationPatch.cs

@@ -87,8 +87,8 @@ private static void RunAfterRoomIsLoaded(NFakeMerchant screen)
                         ?? RitsuGodotNodeFactories.CreateFromScenePath<NMerchantCharacter>(
                             player.Character.MerchantAnimPath, PackedScene.GenEditState.Disabled);
 
-                    characterContainer.AddChildSafely(nMerchantCharacter);
-                    characterContainer.MoveChildSafely(nMerchantCharacter, 0);
+                    RitsuGodotTreeCompat.AddChildSafely(characterContainer, nMerchantCharacter);
+                    RitsuGodotTreeCompat.MoveChildSafely(characterContainer, nMerchantCharacter, 0);
                     nMerchantCharacter.Position = new(num2, -50f * i);
                     if (i > 0)
                         nMerchantCharacter.Modulate = new(0.5f, 0.5f, 0.5f);

Scaffolding/Characters/Patches/NMerchantRoomProceduralCharacterInstantiationPatch.cs

@@ -2,7 +2,6 @@
 using HarmonyLib;
 using MegaCrit.Sts2.Core.Context;
 using MegaCrit.Sts2.Core.Entities.Players;
-using MegaCrit.Sts2.Core.Helpers;
 using MegaCrit.Sts2.Core.Nodes.Rooms;
 using MegaCrit.Sts2.Core.Nodes.Screens.Shops;
 using STS2RitsuLib.Patching.Models;
@@ -79,8 +78,8 @@ private static void RunAfterRoomIsLoaded(NMerchantRoom room)
                         ModWorldSceneVisualNodeFactory.TryInstantiateMerchantCharacter(player.Character)
                         ?? RitsuGodotNodeFactories.CreateFromScenePath<NMerchantCharacter>(
                             player.Character.MerchantAnimPath, PackedScene.GenEditState.Disabled);
-                    characterContainer.AddChildSafely(nMerchantCharacter);
-                    characterContainer.MoveChild(nMerchantCharacter, 0);
+                    RitsuGodotTreeCompat.AddChildSafely(characterContainer, nMerchantCharacter);
+                    RitsuGodotTreeCompat.MoveChildSafely(characterContainer, nMerchantCharacter, 0);
                     nMerchantCharacter.Position = new(num2, -50f * i);
                     if (i > 0)
                         nMerchantCharacter.Modulate = new(0.5f, 0.5f, 0.5f);

Scaffolding/Godot/RitsuGodotTreeCompat.cs

@@ -0,0 +1,49 @@
+using Godot;
+using MegaCrit.Sts2.Core.Nodes;
+
+namespace STS2RitsuLib.Scaffolding.Godot
+{
+    /// <summary>
+    ///     Tree mutations aligned with vanilla <c>GodotTreeExtensions</c> (0.104.x). Game 0.103.2 omits
+    ///     <c>MoveChildSafely</c>; referencing it from mods breaks multi-version builds. Use these helpers instead of
+    ///     calling game extension methods for merchant-booth style layout.
+    /// </summary>
+    public static class RitsuGodotTreeCompat
+    {
+        /// <summary>
+        ///     Same branching as <c>MegaCrit.Sts2.Core.Helpers.GodotTreeExtensions.AddChildSafely</c> on current game
+        ///     branches that ship it.
+        /// </summary>
+        public static void AddChildSafely(Node parent, Node? child)
+        {
+            if (child == null || !GodotObject.IsInstanceValid(parent))
+                return;
+
+            if (NGame.IsMainThread() && (parent.IsNodeReady() || !parent.IsInsideTree()))
+            {
+                parent.AddChild(child);
+                return;
+            }
+
+            parent.CallDeferred(Node.MethodName.AddChild, child);
+        }
+
+        /// <summary>
+        ///     Same branching as <c>MegaCrit.Sts2.Core.Helpers.GodotTreeExtensions.MoveChildSafely</c> where the game
+        ///     provides it (0.104+); self-contained for 0.103.2 reference assemblies.
+        /// </summary>
+        public static void MoveChildSafely(Node parent, Node? child, int index)
+        {
+            if (child == null || !GodotObject.IsInstanceValid(parent))
+                return;
+
+            if (NGame.IsMainThread() && (parent.IsNodeReady() || !parent.IsInsideTree()))
+            {
+                parent.MoveChild(child, index);
+                return;
+            }
+
+            parent.CallDeferred(Node.MethodName.MoveChild, child, index);
+        }
+    }
+}