Batch Drag & Drop Images (#8282)

## Summary

<!-- One sentence describing what changed and why. -->
Added feature to drag and drop multiple images into the UI and connect
them with a Batch Images node with tests to add convenience for users.
Only works with a group of images, mixing files not supported.

## Review Focus
<!-- Critical design decisions or edge cases that need attention -->
I've updated our usage of Litegraph.createNode, honestly, that method is
pretty bad, onNodeCreated option method doesn't even return the node
created. I think I will probably go check out their repo to do a PR over
there. Anyways, I made a createNode method to avoid race conditions when
creating nodes for the paste actions. Will allow us to better
programmatically create nodes that do not have workflows that also need
to be connected to other nodes.

<!-- If this PR fixes an issue, uncomment and update the line below -->

https://www.notion.so/comfy-org/Implement-Multi-image-drag-and-drop-to-canvas-2eb6d73d36508195ad8addfc4367db10

## Screenshots (if applicable)

https://github.com/user-attachments/assets/d4155807-56e2-4e39-8ab1-16eda90f6a53

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8282-Batch-Drag-Drop-Images-2f16d73d365081c1ab31ce9da47a7be5)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: Austin Mroz <austin@comfy.org>

src/utils/litegraphUtil.test.ts

@@ -1,13 +1,97 @@
-import { describe, expect, it } from 'vitest'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
 
+import { LiteGraph } from '@/lib/litegraph/src/litegraph'
+import type {
+  LGraph,
+  LGraphCanvas,
+  LGraphNode
+} from '@/lib/litegraph/src/litegraph'
 import type { ISerialisedGraph } from '@/lib/litegraph/src/types/serialisation'
 import type { IWidget } from '@/lib/litegraph/src/types/widgets'
 import type { InputSpec } from '@/schemas/nodeDef/nodeDefSchemaV2'
 import {
   compressWidgetInputSlots,
+  createNode,
   migrateWidgetsValues
 } from '@/utils/litegraphUtil'
 
+vi.mock('@/lib/litegraph/src/litegraph', () => ({
+  LiteGraph: {
+    createNode: vi.fn()
+  }
+}))
+
+vi.mock('@/platform/updates/common/toastStore', () => ({
+  useToastStore: vi.fn(() => ({
+    addAlert: vi.fn(),
+    add: vi.fn(),
+    remove: vi.fn()
+  }))
+}))
+
+vi.mock('@/i18n', () => ({
+  t: vi.fn((key: string) => key)
+}))
+
+function createMockCanvas(overrides: Partial<LGraphCanvas> = {}): LGraphCanvas {
+  const mockGraph = {
+    add: vi.fn((node) => node),
+    change: vi.fn()
+  } satisfies Partial<LGraph> as unknown as LGraph
+  const mockCanvas: Partial<LGraphCanvas> = {
+    graph_mouse: [100, 200],
+    graph: mockGraph,
+    ...overrides
+  }
+  return mockCanvas as LGraphCanvas
+}
+
+describe('createNode', () => {
+  beforeEach(vi.clearAllMocks)
+
+  it('should create a node successfully', async () => {
+    const mockNode = { pos: [0, 0] }
+    vi.mocked(LiteGraph.createNode).mockReturnValue(mockNode as LGraphNode)
+
+    const mockCanvas = createMockCanvas()
+    const result = await createNode(mockCanvas, 'LoadImage')
+
+    expect(LiteGraph.createNode).toHaveBeenCalledWith('LoadImage')
+    expect(mockNode.pos).toEqual([100, 200])
+    expect(mockCanvas.graph!.add).toHaveBeenCalledWith(mockNode)
+    expect(mockCanvas.graph!.change).toHaveBeenCalled()
+    expect(result).toBe(mockNode)
+  })
+
+  it('should return null when name is empty', async () => {
+    const mockCanvas = createMockCanvas()
+    const result = await createNode(mockCanvas, '')
+
+    expect(LiteGraph.createNode).not.toHaveBeenCalled()
+    expect(result).toBeNull()
+  })
+
+  it('should handle graph being null', async () => {
+    const mockNode = { pos: [0, 0] }
+    const mockCanvas = createMockCanvas({ graph: null })
+    vi.mocked(LiteGraph.createNode).mockReturnValue(mockNode as LGraphNode)
+
+    const result = await createNode(mockCanvas, 'LoadImage')
+
+    expect(mockNode.pos).toEqual([0, 0])
+    expect(result).toBeNull()
+  })
+  it('should set position based on canvas graph_mouse', async () => {
+    const mockCanvas = createMockCanvas({ graph_mouse: [250, 350] })
+    const mockNode = { pos: [0, 0] }
+    vi.mocked(LiteGraph.createNode).mockReturnValue(mockNode as LGraphNode)
+
+    await createNode(mockCanvas, 'LoadAudio')
+
+    expect(mockNode.pos).toEqual([250, 350])
+  })
+})
+
 describe('migrateWidgetsValues', () => {
   it('should remove widget values for forceInput inputs', () => {
     const inputDefs: Record<string, InputSpec> = {