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/components/graph/selectionToolbox/ExecuteButton.test.ts

@@ -1,23 +1,16 @@
 import { mount } from '@vue/test-utils'
-import { createPinia, setActivePinia } from 'pinia'
+import { createTestingPinia } from '@pinia/testing'
+import { setActivePinia } from 'pinia'
 import PrimeVue from 'primevue/config'
 import Tooltip from 'primevue/tooltip'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { createI18n } from 'vue-i18n'
 
 import ExecuteButton from '@/components/graph/selectionToolbox/ExecuteButton.vue'
+import type { LGraphCanvas, LGraphNode } from '@/lib/litegraph/src/litegraph'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { useCommandStore } from '@/stores/commandStore'
 
-// Mock the stores
-vi.mock('@/renderer/core/canvas/canvasStore', () => ({
-  useCanvasStore: vi.fn()
-}))
-
-vi.mock('@/stores/commandStore', () => ({
-  useCommandStore: vi.fn()
-}))
-
 // Mock the utils
 vi.mock('@/utils/litegraphUtil', () => ({
   isLGraphNode: vi.fn((node) => !!node?.type)
@@ -37,10 +30,8 @@ vi.mock('@/composables/graph/useSelectionState', () => ({
 }))
 
 describe('ExecuteButton', () => {
-  let mockCanvas: any
-  let mockCanvasStore: any
-  let mockCommandStore: any
-  let mockSelectedNodes: any[]
+  let mockCanvas: LGraphCanvas
+  let mockSelectedNodes: LGraphNode[]
 
   const i18n = createI18n({
     legacy: false,
@@ -57,27 +48,27 @@ describe('ExecuteButton', () => {
   })
 
   beforeEach(async () => {
-    setActivePinia(createPinia())
+    // Set up Pinia with testing utilities
+    setActivePinia(
+      createTestingPinia({
+        createSpy: vi.fn
+      })
+    )
 
     // Reset mocks
-    mockCanvas = {
+    const partialCanvas: Partial<LGraphCanvas> = {
       setDirty: vi.fn()
     }
+    mockCanvas = partialCanvas as Partial<LGraphCanvas> as LGraphCanvas
 
     mockSelectedNodes = []
 
-    mockCanvasStore = {
-      getCanvas: vi.fn(() => mockCanvas),
-      selectedItems: []
-    }
+    // Get store instances and mock methods
+    const canvasStore = useCanvasStore()
+    const commandStore = useCommandStore()
 
-    mockCommandStore = {
-      execute: vi.fn()
-    }
-
-    // Setup store mocks
-    vi.mocked(useCanvasStore).mockReturnValue(mockCanvasStore as any)
-    vi.mocked(useCommandStore).mockReturnValue(mockCommandStore as any)
+    vi.spyOn(canvasStore, 'getCanvas').mockReturnValue(mockCanvas)
+    vi.spyOn(commandStore, 'execute').mockResolvedValue()
 
     // Update the useSelectionState mock
     const { useSelectionState } = vi.mocked(
@@ -87,7 +78,7 @@ describe('ExecuteButton', () => {
       selectedNodes: {
         value: mockSelectedNodes
       }
-    } as any)
+    } as ReturnType<typeof useSelectionState>)
 
     vi.clearAllMocks()
   })
@@ -114,15 +105,16 @@ describe('ExecuteButton', () => {
 
   describe('Click Handler', () => {
     it('should execute Comfy.QueueSelectedOutputNodes command on click', async () => {
+      const commandStore = useCommandStore()
       const wrapper = mountComponent()
       const button = wrapper.find('button')
 
       await button.trigger('click')
 
-      expect(mockCommandStore.execute).toHaveBeenCalledWith(
+      expect(commandStore.execute).toHaveBeenCalledWith(
         'Comfy.QueueSelectedOutputNodes'
       )
-      expect(mockCommandStore.execute).toHaveBeenCalledTimes(1)
+      expect(commandStore.execute).toHaveBeenCalledTimes(1)
     })
   })
 })