[fix] properly show error states (#5758)

## Summary

I want to take a more general look at `comfyApp.graph.onTrigger` but
this is the cleanest fix I could come up with for #5694.

I will explore simplifying onTrigger in a separate PR.

## Changes

1. Create a `node:slot-errors:changed` trigger.
2. Trigger it if we find any of the node slots have errors.
3. Check each node to see if there is any error present.
4. Add an error class if there are.

## Screenshots (if applicable)

Working error states!

<img width="1049" height="987" alt="Screenshot 2025-09-23 at 8 40 04 PM"
src="https://github.com/user-attachments/assets/30e13283-129c-4d9c-b342-e7037582998a"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5758-fix-properly-show-error-states-2786d73d365081cbbf62c314c7f5f380)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>

src/composables/graph/useGraphNodeManager.ts

@@ -435,6 +435,28 @@ export function useGraphNodeManager(graph: LGraph): GraphNodeManager {
               })
           }
         }
+      } else if (
+        action === 'node:slot-errors:changed' &&
+        param &&
+        typeof param === 'object'
+      ) {
+        const event = param as { nodeId: string | number }
+        const nodeId = String(event.nodeId)
+        const litegraphNode = nodeRefs.get(nodeId)
+        const currentData = vueNodeData.get(nodeId)
+
+        if (litegraphNode && currentData) {
+          // Re-extract slot data with updated hasErrors properties
+          vueNodeData.set(nodeId, {
+            ...currentData,
+            inputs: litegraphNode.inputs
+              ? [...litegraphNode.inputs]
+              : undefined,
+            outputs: litegraphNode.outputs
+              ? [...litegraphNode.outputs]
+              : undefined
+          })
+        }
       }
 
       // Call original trigger handler if it exists