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/platform/workflow/cloud/getWorkflowFromHistory.test.ts

@@ -0,0 +1,111 @@
+import { describe, expect, it, vi } from 'vitest'
+
+import type { ComfyWorkflowJSON } from '@/platform/workflow/validation/schemas/workflowSchema'
+import { getWorkflowFromHistory } from '@/platform/workflow/cloud/getWorkflowFromHistory'
+
+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 mockHistoryResponse = {
+  'test-prompt-id': {
+    prompt: {
+      priority: 1,
+      prompt_id: 'test-prompt-id',
+      extra_data: {
+        client_id: 'test-client',
+        extra_pnginfo: {
+          workflow: mockWorkflow
+        }
+      }
+    },
+    outputs: {},
+    status: {
+      status_str: 'success',
+      completed: true,
+      messages: []
+    }
+  }
+}
+
+describe('getWorkflowFromHistory', () => {
+  it('should fetch workflow from /history_v2/{prompt_id} endpoint', async () => {
+    const mockFetchApi = vi.fn().mockResolvedValue({
+      json: async () => mockHistoryResponse
+    })
+
+    await getWorkflowFromHistory(mockFetchApi, 'test-prompt-id')
+
+    expect(mockFetchApi).toHaveBeenCalledWith('/history_v2/test-prompt-id')
+  })
+
+  it('should extract and return workflow from response', async () => {
+    const mockFetchApi = vi.fn().mockResolvedValue({
+      json: async () => mockHistoryResponse
+    })
+
+    const result = await getWorkflowFromHistory(mockFetchApi, 'test-prompt-id')
+
+    expect(result).toEqual(mockWorkflow)
+  })
+
+  it('should return undefined when prompt_id not found in response', async () => {
+    const mockFetchApi = vi.fn().mockResolvedValue({
+      json: async () => ({})
+    })
+
+    const result = await getWorkflowFromHistory(mockFetchApi, 'nonexistent-id')
+
+    expect(result).toBeUndefined()
+  })
+
+  it('should return undefined when workflow is missing from extra_pnginfo', async () => {
+    const mockFetchApi = vi.fn().mockResolvedValue({
+      json: async () => ({
+        'test-prompt-id': {
+          prompt: {
+            priority: 1,
+            prompt_id: 'test-prompt-id',
+            extra_data: {
+              client_id: 'test-client'
+            }
+          },
+          outputs: {}
+        }
+      })
+    })
+
+    const result = await getWorkflowFromHistory(mockFetchApi, 'test-prompt-id')
+
+    expect(result).toBeUndefined()
+  })
+
+  it('should handle fetch errors gracefully', async () => {
+    const mockFetchApi = vi.fn().mockRejectedValue(new Error('Network error'))
+
+    const result = await getWorkflowFromHistory(mockFetchApi, 'test-prompt-id')
+
+    expect(result).toBeUndefined()
+  })
+
+  it('should handle malformed JSON responses', async () => {
+    const mockFetchApi = vi.fn().mockResolvedValue({
+      json: async () => {
+        throw new Error('Invalid JSON')
+      }
+    })
+
+    const result = await getWorkflowFromHistory(mockFetchApi, 'test-prompt-id')
+
+    expect(result).toBeUndefined()
+  })
+})