[style] Update error/subgraph node footer design with layered overlay approach (#9360)

## Summary

Refactors the error and subgraph node footer UI by extracting a
dedicated `NodeFooter` component and replacing the CSS `outline`
approach with a layered border overlay for selection/executing state
indicators.

## Changes

- **What**: Extracted `NodeFooter.vue` from `LGraphNode.vue` to
encapsulate the footer tab logic (subgraph enter, error, advanced
inputs). Replaced CSS `outline` with an absolutely-positioned border
overlay div for selection and executing state. Added a separate root
border overlay div for the node body border. Removed unused
`isTransparent` function from `colorUtil.ts`.
- **Dependencies**: None

## Review Focus

- The layered overlay approach (`absolute -inset-[3px] border-3`) for
selection/executing outlines vs the previous `outline-3` approach —
ensures the outline renders outside the node bounds correctly including
the footer area
- `NodeFooter` handles 4 cases: subgraph+error (dual tabs), error only,
subgraph only, advanced inputs — verify edge cases render correctly
- Resize handle bottom offset adjustments for nodes with footers
(`hasFooter`)

## Screenshots
<img width="1142" height="603" alt="image"
src="https://github.com/user-attachments/assets/e0d401f0-8516-4f5f-ab77-48a79530f4bd"
/>
<img width="1175" height="577" alt="image"
src="https://github.com/user-attachments/assets/bcf08fff-728a-491c-add9-5b96d2f3bfce"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9360-style-Update-error-subgraph-node-footer-design-with-layered-overlay-approach-3186d73d365081b2ac31f166f4d1944a)
by [Unito](https://www.unito.io)

---------

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

browser_tests/tests/vueNodes/nodeStates/error.spec.ts

@@ -3,7 +3,7 @@ import {
   comfyPageFixture as test
 } from '../../../fixtures/ComfyPage'
 
-const ERROR_CLASS = /border-node-stroke-error/
+const ERROR_CLASS = /ring-destructive-background/
 
 test.describe('Vue Node Error', () => {
   test.beforeEach(async ({ comfyPage }) => {
@@ -18,9 +18,10 @@ test.describe('Vue Node Error', () => {
     await comfyPage.workflow.loadWorkflow('missing/missing_nodes')
 
     // Expect error state on missing unknown node
-    const unknownNode = comfyPage.page.locator('[data-node-id]').filter({
-      hasText: 'UNKNOWN NODE'
-    })
+    const unknownNode = comfyPage.page
+      .locator('[data-node-id]')
+      .filter({ hasText: 'UNKNOWN NODE' })
+      .getByTestId('node-inner-wrapper')
     await expect(unknownNode).toHaveClass(ERROR_CLASS)
   })
 
@@ -31,7 +32,10 @@ test.describe('Vue Node Error', () => {
     await comfyPage.workflow.loadWorkflow('nodes/execution_error')
     await comfyPage.runButton.click()
 
-    const raiseErrorNode = comfyPage.vueNodes.getNodeByTitle('Raise Error')
+    const raiseErrorNode = comfyPage.page
+      .locator('[data-node-id]')
+      .filter({ hasText: 'Raise Error' })
+      .getByTestId('node-inner-wrapper')
     await expect(raiseErrorNode).toHaveClass(ERROR_CLASS)
   })
 })