refactor: Replace deprecated dungeon editor guide with updated documentation

- Deleted the old D1-dungeon-editor-guide.md and F1-dungeon-editor-guide.md files to streamline documentation.
- Introduced a new DUNGEON_EDITOR_GUIDE.md that consolidates features, architecture, and usage instructions for the Dungeon Editor.
- Updated the development guide to include new naming conventions and clarified rendering processes.
- Enhanced the overall structure and content of the documentation to reflect the current production-ready status of the Dungeon Editor.

src/app/editor/dungeon/dungeon_canvas_viewer.cc

@@ -135,6 +135,60 @@ void DungeonCanvasViewer::DrawDungeonCanvas(int room_id) {
   ImGui::EndGroup();
 
   canvas_.DrawBackground();
+  
+  // Add dungeon-specific context menu items
+  canvas_.ClearContextMenuItems();
+  
+  if (rooms_ && rom_->is_loaded()) {
+    auto& room = (*rooms_)[room_id];
+    
+    // Add object placement option
+    canvas_.AddContextMenuItem({
+      ICON_MD_ADD " Place Object",
+      []() {
+        // TODO: Show object palette/selector
+      },
+      "Ctrl+P"
+    });
+    
+    // Add object deletion for selected objects
+    canvas_.AddContextMenuItem({
+      ICON_MD_DELETE " Delete Selected",
+      [this]() {
+        object_interaction_.HandleDeleteSelected();
+      },
+      "Del"
+    });
+    
+    // Add room property quick toggles
+    canvas_.AddContextMenuItem({
+      ICON_MD_LAYERS " Toggle BG1",
+      [this, room_id]() {
+        auto& settings = GetRoomLayerSettings(room_id);
+        settings.bg1_visible = !settings.bg1_visible;
+      },
+      "1"
+    });
+    
+    canvas_.AddContextMenuItem({
+      ICON_MD_LAYERS " Toggle BG2",
+      [this, room_id]() {
+        auto& settings = GetRoomLayerSettings(room_id);
+        settings.bg2_visible = !settings.bg2_visible;
+      },
+      "2"
+    });
+    
+    // Add re-render option
+    canvas_.AddContextMenuItem({
+      ICON_MD_REFRESH " Re-render Room",
+      [&room]() {
+        room.RenderRoomGraphics();
+      },
+      "Ctrl+R"
+    });
+  }
+  
   canvas_.DrawContextMenu();
   
   if (rooms_ && rom_->is_loaded()) {

src/app/editor/dungeon/dungeon_editor_v2.cc

@@ -22,8 +22,7 @@ void DungeonEditorV2::Initialize(gfx::IRenderer* renderer, Rom* rom) {
   // Don't initialize emulator preview yet - ROM might not be loaded
   // Will be initialized in Load() instead
   
-  // Setup docking class for room windows
-  room_window_class_.ClassId = ImGui::GetID("DungeonRoomClass");
+  // Setup docking class for room windows (ImGui::GetID will be called in Update when ImGui is ready)
   room_window_class_.DockingAllowUnclassed = true;  // Room windows can dock with anything
   room_window_class_.DockingAlwaysTabBar = true;    // Always show tabs when multiple rooms
   
@@ -158,6 +157,11 @@ absl::Status DungeonEditorV2::Load() {
 }
 
 absl::Status DungeonEditorV2::Update() {
+  // Initialize docking class ID on first Update (when ImGui is ready)
+  if (room_window_class_.ClassId == 0) {
+    room_window_class_.ClassId = ImGui::GetID("DungeonRoomClass");
+  }
+  
   if (!is_loaded_) {
     // CARD-BASED EDITOR: Create a minimal loading card
     gui::EditorCard loading_card("Dungeon Editor Loading", ICON_MD_CASTLE);