fix: show Missing Nodes dialog for missing node prompt errors (#8511)

## Summary
When a workflow is queued with a missing node type, show the Missing
Nodes dialog instead of a generic error toast. This gives users
actionable options like "Open Manager" and "Install All".

## Changes
- Detect `missing_node_type` error from backend in `queuePrompt()` catch
block
- Construct `MissingNodeType` object with class type and contextual hint
- Reuse existing `showMissingNodesError()` to trigger the dialog

## Dependencies
⚠️ **Requires backend PR:**
https://github.com/Comfy-Org/ComfyUI/pull/12177

The backend PR changes the error type from `invalid_prompt` to
`missing_node_type` and adds `extra_info` with node details.

## Related
- Fixes COM-12528
- Addresses ~49 GitHub issues with confusing "missing class_type" errors

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8511-fix-show-Missing-Nodes-dialog-for-missing-node-prompt-errors-2f96d73d3650812b95f0f08e51abaabb)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

src/workbench/extensions/manager/utils/missingNodeErrorUtil.ts

@@ -0,0 +1,37 @@
+import type { MissingNodeType } from '@/types/comfy'
+
+import type { MissingNodeTypeExtraInfo } from '../types/missingNodeErrorTypes'
+
+/**
+ * Builds a hint string from missing node metadata.
+ * Provides context about which node is missing (title, ID) when available.
+ */
+export function buildMissingNodeHint(
+  nodeTitle: string | null | undefined,
+  classType: string,
+  nodeId: string | undefined
+): string | undefined {
+  const hasTitle = nodeTitle && nodeTitle !== classType
+  if (hasTitle && nodeId) {
+    return `"${nodeTitle}" (Node ID #${nodeId})`
+  } else if (hasTitle) {
+    return `"${nodeTitle}"`
+  } else if (nodeId) {
+    return `Node ID #${nodeId}`
+  }
+  return undefined
+}
+
+/**
+ * Creates a MissingNodeType from backend error extra_info.
+ * Used when the /prompt endpoint returns a missing_node_type error.
+ */
+export function createMissingNodeTypeFromError(
+  extraInfo: MissingNodeTypeExtraInfo
+): MissingNodeType {
+  const classType = extraInfo.class_type ?? 'Unknown'
+  const nodeTitle = extraInfo.node_title ?? classType
+  const hint = buildMissingNodeHint(nodeTitle, classType, extraInfo.node_id)
+
+  return hint ? { type: classType, hint } : classType
+}