Resolve issues with undo with Nodes 2.0 to fix link dragging/rendering (#8808)

## Summary

Resolves the following issue:
1. Enable Nodes 2.0
2. Load default workflow
3. Move any node e.g. VAE decode
4. Undo

All links go invisible, input/output slots no longer function

## Changes

- **What**
- Fixes slot layouts being deleted during undo/redo in
`handleDeleteNode`, which prevented link dragging from nodes after undo.
Vue patches (not remounts) components with the same key, so `onMounted`
never fires to re-register them - these were already being cleared up on
unmounted
- Fixes links disappearing after undo by clearing `pendingSlotSync` when
slot layouts already exist (undo/redo preserved them), rather than
waiting for Vue mounts that do not happen

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8808-Resolve-issues-with-undo-with-Nodes-2-0-to-fix-link-dragging-rendering-3046d73d3650818bbb0adf0104a5792d)
by [Unito](https://www.unito.io)

src/renderer/core/layout/store/layoutStore.test.ts

@@ -1,9 +1,14 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { LiteGraph } from '@/lib/litegraph/src/litegraph'
+import { getSlotKey } from '@/renderer/core/layout/slots/slotIdentifier'
 import { layoutStore } from '@/renderer/core/layout/store/layoutStore'
 import { LayoutSource } from '@/renderer/core/layout/types'
-import type { LayoutChange, NodeLayout } from '@/renderer/core/layout/types'
+import type {
+  LayoutChange,
+  NodeLayout,
+  SlotLayout
+} from '@/renderer/core/layout/types'
 
 describe('layoutStore CRDT operations', () => {
   beforeEach(() => {
@@ -406,4 +411,49 @@ describe('layoutStore CRDT operations', () => {
       LiteGraph.NODE_TITLE_HEIGHT = originalTitleHeight
     }
   })
+
+  it.for([
+    { type: 'input' as const, isInput: true },
+    { type: 'output' as const, isInput: false }
+  ])(
+    'should preserve $type slot layouts when deleting a node',
+    ({ type, isInput }) => {
+      const nodeId = 'slot-persist-node'
+      const layout = createTestNode(nodeId)
+
+      layoutStore.applyOperation({
+        type: 'createNode',
+        entity: 'node',
+        nodeId,
+        layout,
+        timestamp: Date.now(),
+        source: LayoutSource.External,
+        actor: 'test'
+      })
+
+      const slotKey = getSlotKey(nodeId, 0, isInput)
+      const slotLayout: SlotLayout = {
+        nodeId,
+        index: 0,
+        type,
+        position: { x: 110, y: 120 },
+        bounds: { x: 105, y: 115, width: 10, height: 10 }
+      }
+      layoutStore.batchUpdateSlotLayouts([{ key: slotKey, layout: slotLayout }])
+      expect(layoutStore.getSlotLayout(slotKey)).toEqual(slotLayout)
+
+      layoutStore.applyOperation({
+        type: 'deleteNode',
+        entity: 'node',
+        nodeId,
+        previousLayout: layout,
+        timestamp: Date.now(),
+        source: LayoutSource.External,
+        actor: 'test'
+      })
+
+      // Slot layout must survive so Vue-patched components can still drag links
+      expect(layoutStore.getSlotLayout(slotKey)).toEqual(slotLayout)
+    }
+  )
 })

src/renderer/core/layout/store/layoutStore.ts

@@ -151,6 +151,10 @@ class LayoutStoreImpl implements LayoutStore {
     return this._pendingSlotSync
   }
 
+  get hasSlotLayouts(): boolean {
+    return this.slotLayouts.size > 0
+  }
+
   setPendingSlotSync(value: boolean): void {
     this._pendingSlotSync = value
   }
@@ -513,23 +517,6 @@ class LayoutStoreImpl implements LayoutStore {
     }
   }
 
-  /**
-   * Delete all slot layouts for a node
-   */
-  deleteNodeSlotLayouts(nodeId: NodeId): void {
-    const keysToDelete: string[] = []
-    for (const [key, layout] of this.slotLayouts) {
-      if (layout.nodeId === nodeId) {
-        keysToDelete.push(key)
-      }
-    }
-    for (const key of keysToDelete) {
-      this.slotLayouts.delete(key)
-      // Remove from spatial index
-      this.slotSpatialIndex.remove(key)
-    }
-  }
-
   /**
    * Clear all slot layouts and their spatial index (O(1) operations)
    * Used when switching rendering modes (Vue ↔ LiteGraph)
@@ -1117,13 +1104,10 @@ class LayoutStoreImpl implements LayoutStore {
     // During undo/redo, Vue components may still hold references to the old ref.
     // If we delete the trigger, Vue won't be notified when the node is re-created.
     // The trigger will be called in finalizeOperation to notify Vue of the change.
-
+    // We also intentionally do NOT delete slot layouts here for the same reason,
+    // and cleanup is handled by onUnmounted in useSlotElementTracking.
     // Remove from spatial index
     this.spatialIndex.remove(operation.nodeId)
-
-    // Clean up associated slot layouts
-    this.deleteNodeSlotLayouts(operation.nodeId)
-
     // Clean up associated links
     const linksToDelete = this.findLinksConnectedToNode(operation.nodeId)
 

src/renderer/core/layout/types.ts

@@ -302,7 +302,6 @@ export interface LayoutStore {
   deleteLinkLayout(linkId: LinkId): void
   deleteLinkSegmentLayout(linkId: LinkId, rerouteId: RerouteId | null): void
   deleteSlotLayout(key: string): void
-  deleteNodeSlotLayouts(nodeId: NodeId): void
   deleteRerouteLayout(rerouteId: RerouteId): void
   clearAllSlotLayouts(): void