fix: prevent node height shrinking on vueNodes/litegraph mode switch (#8697)

## Summary
Three interacting bugs caused cumulative height loss (~66px per cycle):

1. useVueNodeLifecycle incorrectly subtracted NODE_TITLE_HEIGHT from
LGraphNode.size[1] during layout init, but size[1] is already
content-only (title excluded per LGraphNode.measure()).

2. ensureCorrectLayoutScale added/subtracted NODE_TITLE_HEIGHT in scale
formulas, breaking the round-trip.
Simplified to pure ratio scaling (size * scaleFactor). 
Also set LayoutSource.Canvas before batchUpdateNodeBounds to prevent
stale DOM source from triggering incorrect height normalization.

3. initSizeStyles set --node-height (min-height of the full DOM element
including title) to the content-only layout height.
Added NODE_TITLE_HEIGHT so ResizeObserver captures the correct total
height and normalization recovers the exact content height.

## Screenshots (if applicable)
before

https://github.com/user-attachments/assets/ae41124b-f9e3-4061-8127-eeacddc67a55

after

https://github.com/user-attachments/assets/5ff288a6-73a3-481a-a750-150d9bdbc8fe

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8697-fix-prevent-node-height-shrinking-on-vueNodes-litegraph-mode-switch-2ff6d73d365081c7a2acdc7ec57e2e19)
by [Unito](https://www.unito.io)

---------

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

browser_tests/tests/vueNodes/widgets/int/integerWidget.spec.ts

@@ -31,7 +31,12 @@ test.describe('Vue Integer Widget', () => {
     await expect(seedWidget).toBeVisible()
 
     // Delete the node that is linked to the slot (freeing up the widget)
-    await comfyPage.vueNodes.getNodeByTitle('Int').click()
+    // Click on the header to select the node (clicking center may land on
+    // the widget area where pointerdown.stop prevents node selection)
+    await comfyPage.vueNodes
+      .getNodeByTitle('Int')
+      .locator('.lg-node-header')
+      .click()
     await comfyPage.vueNodes.deleteSelected()
 
     // Test widget works when unlinked