Tool windows redesign and the Novel Editor workspace

Tool windows:
- Every editor (scenario, scene builder, map, interactive objects,
  lighting, catalog export) is rebuilt on the interface ToolWindow chrome
  and the denser ToolTheme: header with title/close, status bar, Ctrl+S,
  dirty-state confirmation.
- Shared building blocks in src/Common: ToolUi (rows, buttons, sections),
  CollapsibleSection, FilteredList, ModFileSelector, DragHandle and
  BackgroundCanvas (scene background with pan/zoom).
- The map, interactive and light editors draw on canvases
  (MapEditorCanvas, InteractiveEditorCanvas, LightEditorCanvas) instead of
  one Control "handle" node per object; the *Handle classes are removed.
- Scenario editor: tab data model (TabData), automatic graph layout
  (ScenarioGraphLayout), file tree/info/thumbnail panel updates.
- Services: ModFileService (mod file listing and writing),
  SceneBackgroundService; MapFileService/ModResourceService follow.
- Catalog export: per-language name/description editing.
- Locale (en/ru) regrouped under tools/*; unused keys removed.

Novel Editor:
- collections/novel_editor.json: a "game" whose entry scene is an
  authoring workspace over the novel engine and the story content.
- NovelEditorHub (scenes/novel_editor_hub.tscn) lists every installed
  tool through IToolProvider.AddMenuButton; ToolsInitializer registers it
  as the logical scene "novel_editor".

src/Common/CollapsibleSection.cs

@@ -0,0 +1,62 @@
+using Cthangover.Core.UI.Theming;
+using Godot;
+
+namespace Cthangover.Tools.Common
+{
+    /// <summary>
+    /// Sidebar section with a clickable uppercase caption (style guide
+    /// <c>.ct-section-title</c> plus a ▸/▾ marker) that shows or hides its
+    /// <see cref="Body"/>. Editors expand the sections relevant to the selected
+    /// object and collapse the rest, so a long property panel stays readable
+    /// without losing access to rarely used fields.
+    /// </summary>
+    public partial class CollapsibleSection : VBoxContainer
+    {
+        private readonly Button _header;
+        private readonly string _title;
+
+        /// <summary>Container for the section's controls.</summary>
+        public VBoxContainer Body { get; }
+
+        /// <summary>Whether the body is shown.</summary>
+        public bool Expanded
+        {
+            get => Body.Visible;
+            set
+            {
+                Body.Visible = value;
+                _header.Text = (value ? "▾  " : "▸  ") + _title;
+            }
+        }
+
+        /// <summary>Creates a section titled by <paramref name="titleKey"/>.</summary>
+        public CollapsibleSection(string titleKey, bool expanded = true)
+        {
+            _title = ToolUi.Tr(titleKey).ToUpperInvariant();
+            AddThemeConstantOverride("separation", UiTokens.Space2);
+
+            _header = new Button
+            {
+                Flat = true,
+                Alignment = HorizontalAlignment.Left,
+                FocusMode = FocusModeEnum.None,
+                MouseDefaultCursorShape = CursorShape.PointingHand
+            };
+            _header.AddThemeFontSizeOverride("font_size", UiTokens.FontSmall);
+            _header.AddThemeColorOverride("font_color", UiTokens.Muted);
+            _header.AddThemeColorOverride("font_hover_color", UiTokens.AccentBright);
+            _header.AddThemeColorOverride("font_pressed_color", UiTokens.Muted);
+            _header.AddThemeStyleboxOverride("normal", new StyleBoxEmpty());
+            _header.AddThemeStyleboxOverride("hover", new StyleBoxEmpty());
+            _header.AddThemeStyleboxOverride("pressed", new StyleBoxEmpty());
+            _header.Pressed += () => Expanded = !Expanded;
+            AddChild(_header);
+
+            Body = new VBoxContainer();
+            Body.AddThemeConstantOverride("separation", UiTokens.Space2);
+            AddChild(Body);
+
+            Expanded = expanded;
+        }
+    }
+}