chore: Assets 디렉토리 구조 정리 및 네이밍 컨벤션 적용

- Assets/_Game/ 하위로 게임 에셋 통합
- External/ 패키지 벤더별 분류 (Synty, Animations, UI)
- 에셋 네이밍 컨벤션 확립 및 적용
  (Data_Skill_, Data_SkillEffect_, Prefab_, Anim_, Model_, BT_ 등)
- pre-commit hook으로 네이밍 컨벤션 자동 검사 추가
- RESTRUCTURE_CHECKLIST.md 작성

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Assets/External/Models/SidekickCharacters/Scripts/Editor/UI/MenuBootstrapController.cs

@@ -0,0 +1,73 @@
+// Copyright (c) 2024 Synty Studios Limited. All rights reserved.
+//
+// Use of this software is subject to the terms and conditions of the Synty Studios End User Licence Agreement (EULA)
+// available at: https://syntystore.com/pages/end-user-licence-agreement
+//
+// For additional details, see the LICENSE.MD file bundled with this software.
+
+#if UNITY_EDITOR
+
+using UnityEditor;
+using UnityEngine;
+
+namespace Synty.SidekickCharacters.UI
+{
+    [InitializeOnLoad]
+    public static class MenuBootstrapController
+    {
+        private const string _AUTO_OPEN_STATE = "syntySkAutoOpenState";
+        private const string _PREFS_CHECK_NAME = "syntySKCheckDependencies";
+
+        private static ModularCharacterWindow _sidekickCharacterWindow;
+        private static bool _openWindowOnStart = true;
+
+        static MenuBootstrapController()
+        {
+            EditorApplication.update += OpenWindowOnStartup;
+        }
+
+        /// <summary>
+        ///     Opens the Character Creator window when Unity starts or the plugin is added to a project.
+        /// </summary>
+        private static void OpenWindowOnStartup()
+        {
+            _openWindowOnStart = EditorPrefs.GetBool(_AUTO_OPEN_STATE, true);
+            EditorApplication.update -= OpenWindowOnStartup;
+            if (_openWindowOnStart)
+            {
+                if (!SessionState.GetBool("FirstInitDone", false))
+                {
+                    ShowSidekickCharacterWindow();
+          
+                    SessionState.SetBool("FirstInitDone", true);
+                }
+                
+            }
+        }
+
+        /// <summary>
+        ///     Creates the Sidekick Character Creator window and adds it to the toolbar.
+        /// </summary>
+        [MenuItem("Synty/Sidekick Character Tool")]
+        public static void ShowSidekickCharacterWindow()
+        {
+            FindSidekickCharacterWindow();
+            _sidekickCharacterWindow.Show();
+        }
+
+        /// <summary>
+        ///     Find the existing Sidekick Character Creator window, or create one if it doesn't exist
+        /// </summary>
+        private static void FindSidekickCharacterWindow()
+        {
+            if (_sidekickCharacterWindow != null)
+            {
+                return;
+            }
+
+            _sidekickCharacterWindow = EditorWindow.GetWindow<ModularCharacterWindow>("Sidekick Character Tool");
+            _sidekickCharacterWindow.minSize = new Vector2(600, 600);
+        }
+    }
+}
+#endif