fix: Vue Node <-> Litegraph node height offset normalization (#6966)

## Summary

Changes the layout store to treat node sizes as body-only measurements
while LiteGraph continues to reason about full heights. DOM-driven
updates are tagged with `LayoutSource.DOM`, which lets the store strip
the title height exactly once before persisting. That classification (a
new mutation source - `LayoutSource.DOM`) is accurate because those
mutations are triggered by the browser’s layout engine via
ResizeObserver, rather than by direct calls into the layout APIs (e.g.,
`moveNodeTo`, `useNodeDrag`). So all sources are:

- `LayoutSource.DOM`: browser layout/ResizeObserver measurements that
include the title bar
- `LayoutSource.Vue`: direct Vue-driven mutations routed through the
layout store
- `LayoutSource.Canvas`: legacy LiteGraph/canvas updates that will be
phased out over time
- `LayoutSource.External`: for multiplayer or syncing with a when going
online after making changes offline (in teams/workspace)

When layout state flows back into LiteGraph we add the title height just
in time for `liteNode.setSize`, so LiteGraph’s rendering stays
unchanged. This makes Vue node resizing and workflow persistence
deterministic - multiline widgets hold their dimensions across reloads
because every path that crosses the layout/LiteGraph boundary performs
the same normalization.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6966-normalize-height-at-sites-2b76d73d365081b6bcb4f4ce6a27663a)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

tests-ui/tests/renderer/core/layout/layoutStore.test.ts

@@ -1,11 +1,9 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
+import { LiteGraph } from '@/lib/litegraph/src/litegraph'
 import { layoutStore } from '@/renderer/core/layout/store/layoutStore'
-import {
-  type LayoutChange,
-  LayoutSource,
-  type NodeLayout
-} from '@/renderer/core/layout/types'
+import { LayoutSource } from '@/renderer/core/layout/types'
+import type { LayoutChange, NodeLayout } from '@/renderer/core/layout/types'
 
 describe('layoutStore CRDT operations', () => {
   beforeEach(() => {
@@ -304,4 +302,108 @@ describe('layoutStore CRDT operations', () => {
     expect(recentOps.length).toBeGreaterThanOrEqual(1)
     expect(recentOps[0].type).toBe('moveNode')
   })
+
+  it('normalizes DOM-sourced heights before storing', () => {
+    const nodeId = 'dom-node'
+    const layout = createTestNode(nodeId)
+
+    layoutStore.applyOperation({
+      type: 'createNode',
+      entity: 'node',
+      nodeId,
+      layout,
+      timestamp: Date.now(),
+      source: LayoutSource.External,
+      actor: 'test'
+    })
+
+    layoutStore.setSource(LayoutSource.DOM)
+    layoutStore.batchUpdateNodeBounds([
+      {
+        nodeId,
+        bounds: {
+          x: layout.bounds.x,
+          y: layout.bounds.y,
+          width: layout.size.width,
+          height: layout.size.height + LiteGraph.NODE_TITLE_HEIGHT
+        }
+      }
+    ])
+
+    const nodeRef = layoutStore.getNodeLayoutRef(nodeId)
+    expect(nodeRef.value?.size.height).toBe(layout.size.height)
+    expect(nodeRef.value?.size.width).toBe(layout.size.width)
+    expect(nodeRef.value?.position).toEqual(layout.position)
+  })
+
+  it('normalizes very small DOM-sourced heights safely', () => {
+    const nodeId = 'small-dom-node'
+    const layout = createTestNode(nodeId)
+    layout.size.height = 10
+
+    layoutStore.applyOperation({
+      type: 'createNode',
+      entity: 'node',
+      nodeId,
+      layout,
+      timestamp: Date.now(),
+      source: LayoutSource.External,
+      actor: 'test'
+    })
+
+    layoutStore.setSource(LayoutSource.DOM)
+    layoutStore.batchUpdateNodeBounds([
+      {
+        nodeId,
+        bounds: {
+          x: layout.bounds.x,
+          y: layout.bounds.y,
+          width: layout.size.width,
+          height: layout.size.height + LiteGraph.NODE_TITLE_HEIGHT
+        }
+      }
+    ])
+
+    const nodeRef = layoutStore.getNodeLayoutRef(nodeId)
+    expect(nodeRef.value?.size.height).toBeGreaterThanOrEqual(0)
+  })
+
+  it('handles undefined NODE_TITLE_HEIGHT without NaN results', () => {
+    const nodeId = 'undefined-title-height'
+    const layout = createTestNode(nodeId)
+
+    layoutStore.applyOperation({
+      type: 'createNode',
+      entity: 'node',
+      nodeId,
+      layout,
+      timestamp: Date.now(),
+      source: LayoutSource.External,
+      actor: 'test'
+    })
+
+    const originalTitleHeight = LiteGraph.NODE_TITLE_HEIGHT
+    // @ts-expect-error – intentionally simulate undefined runtime value
+    LiteGraph.NODE_TITLE_HEIGHT = undefined
+
+    try {
+      layoutStore.setSource(LayoutSource.DOM)
+      layoutStore.batchUpdateNodeBounds([
+        {
+          nodeId,
+          bounds: {
+            x: layout.bounds.x,
+            y: layout.bounds.y,
+            width: layout.size.width,
+            height: layout.size.height
+          }
+        }
+      ])
+
+      const nodeRef = layoutStore.getNodeLayoutRef(nodeId)
+      expect(nodeRef.value?.size.height).toBe(layout.size.height)
+    } finally {
+      LiteGraph.NODE_TITLE_HEIGHT = originalTitleHeight
+    }
+  })
 })

tests-ui/tests/renderer/extensions/vueNodes/composables/useNodeZIndex.test.ts

@@ -5,7 +5,9 @@ import { LayoutSource } from '@/renderer/core/layout/types'
 import { useNodeZIndex } from '@/renderer/extensions/vueNodes/composables/useNodeZIndex'
 
 // Mock the layout mutations module
-vi.mock('@/renderer/core/layout/operations/layoutMutations')
+vi.mock('@/renderer/core/layout/operations/layoutMutations', () => ({
+  useLayoutMutations: vi.fn()
+}))
 
 const mockedUseLayoutMutations = vi.mocked(useLayoutMutations)