refactor(editor): streamline ImGui card management across various editors

- Refactored multiple editor classes to ensure that ImGui::End() is always called after ImGui::Begin(), enhancing state management and preventing potential rendering issues.
- Updated the DungeonEditor, GraphicsEditor, ScreenEditor, MessageEditor, MusicEditor, and SpriteEditor to follow this pattern, improving code consistency and reliability.

Benefits:
- Improves the stability of the editor UI by ensuring proper handling of ImGui state.
- Enhances code readability and maintainability by standardizing the usage of ImGui functions across different editor components.

src/app/editor/sprite/sprite_editor.cc

@@ -57,15 +57,16 @@ absl::Status SpriteEditor::Update() {
   custom_card.SetDefaultSize(800, 600);
 
   // Get visibility flags from card manager and pass to Begin()
+  // Always call End() after Begin() - End() handles ImGui state safely
   if (vanilla_card.Begin(card_manager.GetVisibilityFlag("sprite.vanilla_editor"))) {
     DrawVanillaSpriteEditor();
-    vanilla_card.End();
   }
+  vanilla_card.End();
 
   if (custom_card.Begin(card_manager.GetVisibilityFlag("sprite.custom_editor"))) {
     DrawCustomSprites();
-    custom_card.End();
   }
+  custom_card.End();
 
   return status_.ok() ? absl::OkStatus() : status_;
 }