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)

src/platform/remote/comfyui/history/reconciliation.ts

@@ -13,11 +13,6 @@
 import { isCloud } from '@/platform/distribution/types'
 import type { TaskItem } from '@/schemas/apiSchema'
 
-interface ReconciliationResult {
-  /** All items to display, sorted by queueIndex descending (newest first) */
-  items: TaskItem[]
-}
-
 /**
  * V1 reconciliation: QueueIndex-based filtering works because V1 has stable,
  * monotonically increasing queue indices.
@@ -25,13 +20,15 @@ interface ReconciliationResult {
  * Sort order: Sorts serverHistory by queueIndex descending (newest first) to ensure
  * consistent ordering. JavaScript .filter() maintains iteration order, so filtered
  * results remain sorted. clientHistory is assumed already sorted from previous update.
+ *
+ * @returns All items to display, sorted by queueIndex descending (newest first)
  */
 function reconcileHistoryV1(
   serverHistory: TaskItem[],
   clientHistory: TaskItem[],
   maxItems: number,
   lastKnownQueueIndex: number | undefined
-): ReconciliationResult {
+): TaskItem[] {
   const sortedServerHistory = serverHistory.sort(
     (a, b) => b.prompt[0] - a.prompt[0]
   )
@@ -53,13 +50,9 @@ function reconcileHistoryV1(
   )
 
   // Merge new and reused items, sort by queueIndex descending, limit to maxItems
-  const allItems = [...itemsAddedSinceLastSync, ...clientItemsStillOnServer]
+  return [...itemsAddedSinceLastSync, ...clientItemsStillOnServer]
     .sort((a, b) => b.prompt[0] - a.prompt[0])
     .slice(0, maxItems)
-
-  return {
-    items: allItems
-  }
 }
 
 /**
@@ -69,12 +62,14 @@ function reconcileHistoryV1(
  * Sort order: Sorts serverHistory by queueIndex descending (newest first) to ensure
  * consistent ordering. JavaScript .filter() maintains iteration order, so filtered
  * results remain sorted. clientHistory is assumed already sorted from previous update.
+ *
+ * @returns All items to display, sorted by queueIndex descending (newest first)
  */
 function reconcileHistoryV2(
   serverHistory: TaskItem[],
   clientHistory: TaskItem[],
   maxItems: number
-): ReconciliationResult {
+): TaskItem[] {
   const sortedServerHistory = serverHistory.sort(
     (a, b) => b.prompt[0] - a.prompt[0]
   )
@@ -84,29 +79,18 @@ function reconcileHistoryV2(
   )
   const clientPromptIds = new Set(clientHistory.map((item) => item.prompt[1]))
 
-  const newPromptIds = new Set(
-    [...serverPromptIds].filter((id) => !clientPromptIds.has(id))
+  const newItems = sortedServerHistory.filter(
+    (item) => !clientPromptIds.has(item.prompt[1])
   )
 
-  const newItems = sortedServerHistory.filter((item) =>
-    newPromptIds.has(item.prompt[1])
-  )
-
-  const retainedPromptIds = new Set(
-    [...serverPromptIds].filter((id) => clientPromptIds.has(id))
-  )
   const clientItemsStillOnServer = clientHistory.filter((item) =>
-    retainedPromptIds.has(item.prompt[1])
+    serverPromptIds.has(item.prompt[1])
   )
 
   // Merge new and reused items, sort by queueIndex descending, limit to maxItems
-  const allItems = [...newItems, ...clientItemsStillOnServer]
+  return [...newItems, ...clientItemsStillOnServer]
     .sort((a, b) => b.prompt[0] - a.prompt[0])
     .slice(0, maxItems)
-
-  return {
-    items: allItems
-  }
 }
 
 /**
@@ -125,7 +109,7 @@ export function reconcileHistory(
   clientHistory: TaskItem[],
   maxItems: number,
   lastKnownQueueIndex?: number
-): ReconciliationResult {
+): TaskItem[] {
   if (isCloud) {
     return reconcileHistoryV2(serverHistory, clientHistory, maxItems)
   }

src/platform/workflow/cloud/getWorkflowFromHistory.ts

@@ -0,0 +1,21 @@
+import type { ComfyWorkflowJSON } from '@/platform/workflow/validation/schemas/workflowSchema'
+import type { PromptId } from '@/schemas/apiSchema'
+
+export async function getWorkflowFromHistory(
+  fetchApi: (url: string) => Promise<Response>,
+  promptId: PromptId
+): Promise<ComfyWorkflowJSON | undefined> {
+  try {
+    const res = await fetchApi(`/history_v2/${promptId}`)
+    const json = await res.json()
+
+    const historyItem = json[promptId]
+    if (!historyItem) return undefined
+
+    const workflow = historyItem.prompt?.extra_data?.extra_pnginfo?.workflow
+    return workflow ?? undefined
+  } catch (error) {
+    console.error(`Failed to fetch workflow for prompt ${promptId}:`, error)
+    return undefined
+  }
+}

src/platform/workflow/cloud/index.ts

@@ -0,0 +1,10 @@
+/**
+ * Cloud: Fetches workflow by prompt_id. Desktop: Returns undefined (workflows already in history).
+ */
+import { isCloud } from '@/platform/distribution/types'
+
+import { getWorkflowFromHistory as cloudImpl } from './getWorkflowFromHistory'
+
+export const getWorkflowFromHistory = isCloud
+  ? cloudImpl
+  : async () => undefined