feat(historyV2): load workflows for images (#6384)

## Summary

Hooked up the "Load Workflow" action to our `history_v2` API.

Note: Our cloud envs were being stress tested right now so images are
loading at time of recording. Images were loading for me during
development before I had time to create the video.


## Screenshots 📷 



https://github.com/user-attachments/assets/02145504-ceae-497b-9049-553796d698da



┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6384-Feat-history-v2-workflows-29b6d73d365081bcb706fe799b8ce66a)
by [Unito](https://www.unito.io)

tests-ui/tests/stores/queueStore.loadWorkflow.test.ts

@@ -0,0 +1,175 @@
+import { createPinia, setActivePinia } from 'pinia'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import type { ComfyApp } from '@/scripts/app'
+import type { ComfyWorkflowJSON } from '@/platform/workflow/validation/schemas/workflowSchema'
+import { TaskItemImpl } from '@/stores/queueStore'
+import * as getWorkflowModule from '@/platform/workflow/cloud'
+
+vi.mock('@/platform/distribution/types', () => ({
+  isCloud: true
+}))
+
+vi.mock('@/services/extensionService', () => ({
+  useExtensionService: vi.fn(() => ({
+    invokeExtensions: vi.fn()
+  }))
+}))
+
+const mockWorkflow: ComfyWorkflowJSON = {
+  id: 'test-workflow-id',
+  revision: 0,
+  last_node_id: 5,
+  last_link_id: 3,
+  nodes: [],
+  links: [],
+  groups: [],
+  config: {},
+  extra: {},
+  version: 0.4
+}
+
+const createHistoryTaskWithWorkflow = (): TaskItemImpl => {
+  return new TaskItemImpl(
+    'History',
+    [
+      0, // queueIndex
+      'test-prompt-id', // promptId
+      {}, // promptInputs
+      {
+        client_id: 'test-client',
+        extra_pnginfo: {
+          workflow: mockWorkflow
+        }
+      },
+      [] // outputsToExecute
+    ],
+    {
+      status_str: 'success',
+      completed: true,
+      messages: []
+    },
+    {} // outputs
+  )
+}
+
+const createHistoryTaskWithoutWorkflow = (): TaskItemImpl => {
+  return new TaskItemImpl(
+    'History',
+    [
+      0,
+      'test-prompt-id',
+      {},
+      {
+        client_id: 'test-client'
+        // No extra_pnginfo.workflow
+      },
+      []
+    ],
+    {
+      status_str: 'success',
+      completed: true,
+      messages: []
+    },
+    {}
+  )
+}
+
+describe('TaskItemImpl.loadWorkflow - cloud history workflow fetching', () => {
+  let mockApp: ComfyApp
+  let mockFetchApi: ReturnType<typeof vi.fn>
+
+  beforeEach(() => {
+    setActivePinia(createPinia())
+    vi.clearAllMocks()
+
+    mockFetchApi = vi.fn()
+    mockApp = {
+      loadGraphData: vi.fn(),
+      nodeOutputs: {},
+      api: {
+        fetchApi: mockFetchApi
+      }
+    } as unknown as ComfyApp
+
+    vi.spyOn(getWorkflowModule, 'getWorkflowFromHistory')
+  })
+
+  it('should load workflow directly when workflow is in extra_pnginfo', async () => {
+    const task = createHistoryTaskWithWorkflow()
+
+    await task.loadWorkflow(mockApp)
+
+    expect(mockApp.loadGraphData).toHaveBeenCalledWith(mockWorkflow)
+    expect(mockFetchApi).not.toHaveBeenCalled()
+  })
+
+  it('should fetch workflow from cloud when workflow is missing from history task', async () => {
+    const task = createHistoryTaskWithoutWorkflow()
+
+    // Mock getWorkflowFromHistory to return workflow
+    vi.spyOn(getWorkflowModule, 'getWorkflowFromHistory').mockResolvedValue(
+      mockWorkflow
+    )
+
+    await task.loadWorkflow(mockApp)
+
+    expect(getWorkflowModule.getWorkflowFromHistory).toHaveBeenCalledWith(
+      expect.any(Function),
+      'test-prompt-id'
+    )
+    expect(mockApp.loadGraphData).toHaveBeenCalledWith(mockWorkflow)
+  })
+
+  it('should not load workflow when fetch returns undefined', async () => {
+    const task = createHistoryTaskWithoutWorkflow()
+
+    vi.spyOn(getWorkflowModule, 'getWorkflowFromHistory').mockResolvedValue(
+      undefined
+    )
+
+    await task.loadWorkflow(mockApp)
+
+    expect(getWorkflowModule.getWorkflowFromHistory).toHaveBeenCalled()
+    expect(mockApp.loadGraphData).not.toHaveBeenCalled()
+  })
+
+  it('should only fetch for history tasks, not running tasks', async () => {
+    const runningTask = new TaskItemImpl(
+      'Running',
+      [
+        0,
+        'test-prompt-id',
+        {},
+        {
+          client_id: 'test-client'
+        },
+        []
+      ],
+      undefined,
+      {}
+    )
+
+    vi.spyOn(getWorkflowModule, 'getWorkflowFromHistory').mockResolvedValue(
+      mockWorkflow
+    )
+
+    await runningTask.loadWorkflow(mockApp)
+
+    expect(getWorkflowModule.getWorkflowFromHistory).not.toHaveBeenCalled()
+    expect(mockApp.loadGraphData).not.toHaveBeenCalled()
+  })
+
+  it('should handle fetch errors gracefully by returning undefined', async () => {
+    const task = createHistoryTaskWithoutWorkflow()
+
+    vi.spyOn(getWorkflowModule, 'getWorkflowFromHistory').mockResolvedValue(
+      undefined
+    )
+
+    await task.loadWorkflow(mockApp)
+
+    expect(getWorkflowModule.getWorkflowFromHistory).toHaveBeenCalled()
+    expect(mockApp.loadGraphData).not.toHaveBeenCalled()
+  })
+})