refactor: eliminate unsafe type assertions from Group 2 test files (#8258)

## Summary
Improved type safety in test files by eliminating unsafe type assertions
and adopting official testing patterns. Reduced unsafe `as unknown as`
type assertions and eliminated all `null!` assertions.

## Changes
- **Adopted @pinia/testing patterns**
- Replaced manual Pinia store mocking with `createTestingPinia()` in
`useSelectionState.test.ts`
  - Eliminated ~120 lines of mock boilerplate
- Created `createMockSettingStore()` helper to replace duplicated store
mocks in `useCoreCommands.test.ts`

- **Eliminated unsafe null assertions**
- Created explicit `MockMaskEditorStore` interface with proper nullable
types in `useCanvasTools.test.ts`
- Replaced `null!` initializations with `null` and used `!` at point of
use or `?.` for optional chaining

- **Made partial mock intent explicit**
- Updated test utilities in `litegraphTestUtils.ts` to use explicit
`Partial<T>` typing
- Changed cast pattern from `as T` to `as Partial<T> as T` to show
incomplete mock intent
- Applied to `createMockLGraphNode()`, `createMockPositionable()`, and
`createMockLGraphGroup()`

- **Created centralized mock utilities** in
`src/utils/__tests__/litegraphTestUtils.ts`
- `createMockLGraphNode()`, `createMockPositionable()`,
`createMockLGraphGroup()`, `createMockSubgraphNode()`
  - Updated 8+ test files to use centralized utilities
- Used union types `Partial<T> | Record<string, unknown>` for flexible
mock creation

## Results
- ✅ 0 typecheck errors
- ✅ 0 lint errors  
- ✅ All tests passing in modified files
- ✅ Eliminated all `null!` assertions
- ✅ Reduced unsafe double-cast patterns significantly

## Files Modified (18)
- `src/components/graph/SelectionToolbox.test.ts`
-
`src/components/graph/selectionToolbox/{BypassButton,ColorPickerButton,ExecuteButton}.test.ts`
- `src/components/sidebar/tabs/queue/ResultGallery.test.ts`
- `src/composables/canvas/useSelectedLiteGraphItems.test.ts`
- `src/composables/graph/{useGraphHierarchy,useSelectionState}.test.ts`
-
`src/composables/maskeditor/{useCanvasHistory,useCanvasManager,useCanvasTools,useCanvasTransform}.test.ts`
- `src/composables/node/{useNodePricing,useWatchWidget}.test.ts`
- `src/composables/{useBrowserTabTitle,useCoreCommands}.test.ts`
- `src/utils/__tests__/litegraphTestUtils.ts`

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8258-refactor-eliminate-unsafe-type-assertions-from-Group-2-test-files-2f16d73d365081549c65fd546cc7c765)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: AustinMroz <austin@comfy.org>
Co-authored-by: Christian Byrne <cbyrne@comfy.org>
Co-authored-by: Benjamin Lu <benjaminlu1107@gmail.com>

src/composables/maskeditor/useImageLoader.test.ts

@@ -2,22 +2,39 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { useImageLoader } from '@/composables/maskeditor/useImageLoader'
 
+type MockStore = {
+  imgCanvas: HTMLCanvasElement | null
+  maskCanvas: HTMLCanvasElement | null
+  rgbCanvas: HTMLCanvasElement | null
+  imgCtx: CanvasRenderingContext2D | null
+  maskCtx: CanvasRenderingContext2D | null
+  image: HTMLImageElement | null
+}
+
+type MockDataStore = {
+  inputData: {
+    baseLayer: { image: HTMLImageElement }
+    maskLayer: { image: HTMLImageElement }
+    paintLayer: { image: HTMLImageElement } | null
+  } | null
+}
+
 const mockCanvasManager = {
   invalidateCanvas: vi.fn().mockResolvedValue(undefined),
   updateMaskColor: vi.fn().mockResolvedValue(undefined)
 }
 
-const mockStore = {
-  imgCanvas: null as any,
-  maskCanvas: null as any,
-  rgbCanvas: null as any,
-  imgCtx: null as any,
-  maskCtx: null as any,
-  image: null as any
+const mockStore: MockStore = {
+  imgCanvas: null,
+  maskCanvas: null,
+  rgbCanvas: null,
+  imgCtx: null,
+  maskCtx: null,
+  image: null
 }
 
-const mockDataStore = {
-  inputData: null as any
+const mockDataStore: MockDataStore = {
+  inputData: null
 }
 
 vi.mock('@/stores/maskEditorStore', () => ({
@@ -33,7 +50,8 @@ vi.mock('@/composables/maskeditor/useCanvasManager', () => ({
 }))
 
 vi.mock('@vueuse/core', () => ({
-  createSharedComposable: (fn: any) => fn
+  createSharedComposable: <T extends (...args: unknown[]) => unknown>(fn: T) =>
+    fn
 }))
 
 describe('useImageLoader', () => {
@@ -61,26 +79,26 @@ describe('useImageLoader', () => {
 
     mockStore.imgCtx = {
       clearRect: vi.fn()
-    }
+    } as Partial<CanvasRenderingContext2D> as CanvasRenderingContext2D
 
     mockStore.maskCtx = {
       clearRect: vi.fn()
-    }
+    } as Partial<CanvasRenderingContext2D> as CanvasRenderingContext2D
 
     mockStore.imgCanvas = {
       width: 0,
       height: 0
-    }
+    } as Partial<HTMLCanvasElement> as HTMLCanvasElement
 
     mockStore.maskCanvas = {
       width: 0,
       height: 0
-    }
+    } as Partial<HTMLCanvasElement> as HTMLCanvasElement
 
     mockStore.rgbCanvas = {
       width: 0,
       height: 0
-    }
+    } as Partial<HTMLCanvasElement> as HTMLCanvasElement
 
     mockDataStore.inputData = {
       baseLayer: { image: mockBaseImage },
@@ -104,10 +122,10 @@ describe('useImageLoader', () => {
 
       await loader.loadImages()
 
-      expect(mockStore.maskCanvas.width).toBe(512)
-      expect(mockStore.maskCanvas.height).toBe(512)
-      expect(mockStore.rgbCanvas.width).toBe(512)
-      expect(mockStore.rgbCanvas.height).toBe(512)
+      expect(mockStore.maskCanvas?.width).toBe(512)
+      expect(mockStore.maskCanvas?.height).toBe(512)
+      expect(mockStore.rgbCanvas?.width).toBe(512)
+      expect(mockStore.rgbCanvas?.height).toBe(512)
     })
 
     it('should clear canvas contexts', async () => {
@@ -115,8 +133,8 @@ describe('useImageLoader', () => {
 
       await loader.loadImages()
 
-      expect(mockStore.imgCtx.clearRect).toHaveBeenCalledWith(0, 0, 0, 0)
-      expect(mockStore.maskCtx.clearRect).toHaveBeenCalledWith(0, 0, 0, 0)
+      expect(mockStore.imgCtx?.clearRect).toHaveBeenCalledWith(0, 0, 0, 0)
+      expect(mockStore.maskCtx?.clearRect).toHaveBeenCalledWith(0, 0, 0, 0)
     })
 
     it('should call canvasManager methods', async () => {
@@ -188,10 +206,10 @@ describe('useImageLoader', () => {
 
       await loader.loadImages()
 
-      expect(mockStore.maskCanvas.width).toBe(1024)
-      expect(mockStore.maskCanvas.height).toBe(768)
-      expect(mockStore.rgbCanvas.width).toBe(1024)
-      expect(mockStore.rgbCanvas.height).toBe(768)
+      expect(mockStore.maskCanvas?.width).toBe(1024)
+      expect(mockStore.maskCanvas?.height).toBe(768)
+      expect(mockStore.rgbCanvas?.width).toBe(1024)
+      expect(mockStore.rgbCanvas?.height).toBe(768)
     })
   })
 })