feat: Enhance emulator functionality with card registration and UI improvements

- Registered multiple emulator cards (CPU Debugger, Memory Viewer, PPU Viewer, Audio Mixer) with the EditorCardManager for improved access and organization.
- Updated EditorManager to support the new Emulator editor type in context-sensitive card controls.
- Improved GraphicsEditor loading process with enhanced logging and palette management for graphics sheets.
- Refactored MessageEditor to streamline font bitmap creation and texture queuing, ensuring better performance and clarity in the rendering loop.

src/app/editor/editor_manager.cc

@@ -952,6 +952,12 @@ void EditorManager::DrawContextSensitiveCardControl() {
     case EditorType::kAssembly:
       // Assembly editor uses dynamic file tabs
       return;
+    case EditorType::kEmulator:
+      category = "Emulator";
+      break;
+    case EditorType::kMusic:
+      // Music editor doesn't use cards yet
+      return;
     default:
       return;  // No cards for this editor type
   }