test: add regression tests for subgraph slot label propagation (#10013)

## Summary

Add regression tests for subgraph slot label propagation. The
OutputSlot.vue fix (adding `slotData.label` to the display template) was
already merged via another PR — this adds tests to prevent future
regressions.

## Changes

- **What**: Two new test files covering the label/localized_name
fallback chain in OutputSlot.vue and SubgraphNode label propagation
through configure() and rename event paths.

## Review Focus

Tests only — no production code changes. Verifies that renamed subgraph
inputs/outputs display correctly in Nodes 2.0 mode.

Fixes #9998

<!-- Pipeline-Ticket: 7d887122-eea5-45f1-b6eb-aed94f708555 -->

src/lib/litegraph/src/subgraph/SubgraphNode.test.ts

@@ -958,3 +958,69 @@ describe('SubgraphNode promotion view keys', () => {
     expect(firstKey).not.toBe(secondKey)
   })
 })
+
+describe('SubgraphNode label propagation', () => {
+  it('should preserve input labels from configure path', () => {
+    const subgraph = createTestSubgraph({
+      inputs: [{ name: 'steps', type: 'number' }]
+    })
+    subgraph.inputs[0].label = 'Steps Count'
+
+    const subgraphNode = createTestSubgraphNode(subgraph)
+
+    expect(subgraphNode.inputs[0].label).toBe('Steps Count')
+    expect(subgraphNode.inputs[0].name).toBe('steps')
+  })
+
+  it('should preserve output labels from configure path', () => {
+    const subgraph = createTestSubgraph({
+      outputs: [{ name: 'result', type: 'number' }]
+    })
+    subgraph.outputs[0].label = 'Final Result'
+
+    const subgraphNode = createTestSubgraphNode(subgraph)
+
+    expect(subgraphNode.outputs[0].label).toBe('Final Result')
+    expect(subgraphNode.outputs[0].name).toBe('result')
+  })
+
+  it('should propagate label via renaming-input event', () => {
+    const subgraph = createTestSubgraph()
+    const subgraphNode = createTestSubgraphNode(subgraph)
+
+    subgraph.addInput('steps', 'number')
+    expect(subgraphNode.inputs[0].label).toBeUndefined()
+
+    subgraph.renameInput(subgraph.inputs[0], 'Steps Count')
+
+    expect(subgraphNode.inputs[0].label).toBe('Steps Count')
+    expect(subgraphNode.inputs[0].name).toBe('steps')
+  })
+
+  it('should propagate label via renaming-output event', () => {
+    const subgraph = createTestSubgraph()
+    const subgraphNode = createTestSubgraphNode(subgraph)
+
+    subgraph.addOutput('result', 'number')
+    expect(subgraphNode.outputs[0].label).toBeUndefined()
+
+    subgraph.renameOutput(subgraph.outputs[0], 'Final Result')
+
+    expect(subgraphNode.outputs[0].label).toBe('Final Result')
+    expect(subgraphNode.outputs[0].name).toBe('result')
+  })
+
+  it('should preserve localized_name from configure path', () => {
+    const subgraph = createTestSubgraph({
+      inputs: [{ name: 'steps', type: 'number' }],
+      outputs: [{ name: 'result', type: 'number' }]
+    })
+    subgraph.inputs[0].localized_name = 'ステップ'
+    subgraph.outputs[0].localized_name = '結果'
+
+    const subgraphNode = createTestSubgraphNode(subgraph)
+
+    expect(subgraphNode.inputs[0].localized_name).toBe('ステップ')
+    expect(subgraphNode.outputs[0].localized_name).toBe('結果')
+  })
+})

src/renderer/extensions/vueNodes/components/OutputSlot.test.ts

@@ -0,0 +1,104 @@
+import { mount } from '@vue/test-utils'
+import { describe, expect, it, vi } from 'vitest'
+import { defineComponent } from 'vue'
+import { createI18n } from 'vue-i18n'
+
+import type { INodeSlot } from '@/lib/litegraph/src/litegraph'
+import enMessages from '@/locales/en/main.json' with { type: 'json' }
+
+import OutputSlot from './OutputSlot.vue'
+
+vi.mock('@/composables/useErrorHandling', () => ({
+  useErrorHandling: () => ({ toastErrorHandler: vi.fn() })
+}))
+
+vi.mock('@/renderer/core/canvas/links/slotLinkDragUIState', () => ({
+  useSlotLinkDragUIState: () => ({
+    state: { active: false, compatible: new Map() }
+  })
+}))
+
+vi.mock('@/renderer/extensions/vueNodes/composables/useNodeTooltips', () => ({
+  useNodeTooltips: () => ({
+    getOutputSlotTooltip: () => '',
+    createTooltipConfig: (text: string) => ({ value: text })
+  })
+}))
+
+vi.mock(
+  '@/renderer/extensions/vueNodes/composables/useSlotElementTracking',
+  () => ({ useSlotElementTracking: vi.fn() })
+)
+
+vi.mock(
+  '@/renderer/extensions/vueNodes/composables/useSlotLinkInteraction',
+  () => ({
+    useSlotLinkInteraction: () => ({ onPointerDown: vi.fn() })
+  })
+)
+
+vi.mock('@/renderer/core/layout/slots/slotIdentifier', () => ({
+  getSlotKey: () => 'mock-key'
+}))
+
+const SlotConnectionDotStub = defineComponent({
+  name: 'SlotConnectionDot',
+  template: '<div class="stub-dot" />'
+})
+
+const i18n = createI18n({
+  legacy: false,
+  locale: 'en',
+  messages: { en: enMessages }
+})
+
+function mountOutputSlot(slotData: Partial<INodeSlot>, index = 0) {
+  return mount(OutputSlot, {
+    props: {
+      slotData: { type: '*', ...slotData } as INodeSlot,
+      index,
+      nodeId: 'test-node'
+    },
+    global: {
+      plugins: [i18n],
+      directives: { tooltip: {} },
+      stubs: { SlotConnectionDot: SlotConnectionDotStub }
+    }
+  })
+}
+
+describe('OutputSlot', () => {
+  it('renders label when present on slotData', () => {
+    const wrapper = mountOutputSlot({
+      name: 'internal_name',
+      localized_name: 'Localized Name',
+      label: 'My Custom Label'
+    })
+
+    expect(wrapper.text()).toContain('My Custom Label')
+    expect(wrapper.text()).not.toContain('internal_name')
+    expect(wrapper.text()).not.toContain('Localized Name')
+  })
+
+  it('falls back to localized_name when label is absent', () => {
+    const wrapper = mountOutputSlot({
+      name: 'internal_name',
+      localized_name: 'Localized Name'
+    })
+
+    expect(wrapper.text()).toContain('Localized Name')
+    expect(wrapper.text()).not.toContain('internal_name')
+  })
+
+  it('falls back to name when label and localized_name are absent', () => {
+    const wrapper = mountOutputSlot({ name: 'internal_name' })
+
+    expect(wrapper.text()).toContain('internal_name')
+  })
+
+  it('falls back to "Output N" when all names are absent', () => {
+    const wrapper = mountOutputSlot({ name: undefined }, 2)
+
+    expect(wrapper.text()).toContain('Output 2')
+  })
+})