Fix error handling UX: always show diagram pane on render errors

When Mermaid rendering fails, the error message is displayed in the diagram pane.
Previously, if the user had selected 'code' view, they wouldn't see the error message.
Now the view is always switched to 'diagram' on rendering errors to ensure users
are notified of failures, improving the user experience.

Author: harley

src/contentScript/index.ts

@@ -314,11 +314,7 @@ async function renderBlock(block: MermaidBlock) {
     updateDownloadButtons(registry)
     cleanupGhostNodes(renderId, diagramHost.ownerDocument)
 
-    if (registry.userSelectedView === 'code') {
-      registry.setView('code')
-    } else {
-      registry.setView('diagram')
-    }
+    registry.setView('diagram')
   }
 }