Road to No explicit any Part 8 (Group 3): Improve type safety in Group 3 test mocks (#8304)

## Summary

- Eliminated all `as unknown as` type assertions from Group 3 test files
- Created reusable factory functions in `litegraphTestUtils.ts` for
better type safety
- Improved test mock composition using `Partial` types with single `as`
casts
- Fixed LGraphNode tests to use proper API methods instead of direct
property assignment

## Changes by Category

### New Factory Functions in `litegraphTestUtils.ts`

- `createMockLGraphNodeWithArrayBoundingRect()` - Creates LGraphNode
with proper boundingRect for position tests
- `createMockFileList()` - Creates mock FileList with proper structure
including `item()` method

### Test File Improvements

**Composables:**
- `useLoad3dDrag.test.ts` - Used `createMockFileList` factory
- `useLoad3dViewer.test.ts` - Created local `MockSceneManager` interface
with proper typing

**LiteGraph Tests:**
- `LGraphNode.test.ts` - Replaced direct `boundingRect` assignments with
`updateArea()` calls
- `LinkConnector.test.ts` - Improved mock composition with proper
Partial types
- `ToOutputRenderLink.test.ts` - Added `MockEvents` interface for
type-safe event mocking
- Updated integration and core tests to use new factory functions

**Extension Tests:**
- `contextMenuFilter.test.ts` - Updated menu factories to accept
`(IContextMenuValue | null)[]`

## Type Safety Improvements

- Zero `as unknown as` instances (was: multiple instances across 17
files)
- All mocks use proper `Partial<T>` composition with single `as T` casts
- Improved IntelliSense and type checking in test files
- Centralized mock creation reduces duplication and improves
maintainability

## Test Plan

- ✅ All TypeScript type checks pass
- ✅ ESLint passes with no new errors  
- ✅ Pre-commit hooks (format, lint, typecheck) all pass
- ✅ Knip unused export check passes
- ✅ No behavioral changes to actual tests (only type improvements)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8304-Road-to-No-explicit-any-Improve-type-safety-in-Group-3-test-mocks-2f36d73d365081ab841de96e5f01306d)
by [Unito](https://www.unito.io)

src/utils/__tests__/litegraphTestUtils.ts

@@ -1,11 +1,17 @@
-import type { Positionable } from '@/lib/litegraph/src/interfaces'
+import type {
+  INodeInputSlot,
+  INodeOutputSlot,
+  Positionable
+} from '@/lib/litegraph/src/interfaces'
 import { Rectangle } from '@/lib/litegraph/src/infrastructure/Rectangle'
 import type {
+  CanvasPointerEvent,
+  LGraph,
   LGraphCanvas,
   LGraphGroup,
-  LGraphNode
+  LinkNetwork
 } from '@/lib/litegraph/src/litegraph'
-import { LGraphEventMode } from '@/lib/litegraph/src/litegraph'
+import { LGraphEventMode, LGraphNode } from '@/lib/litegraph/src/litegraph'
 import { vi } from 'vitest'
 
 /**
@@ -84,3 +90,114 @@ export function createMockCanvas(
     ...overrides
   } as LGraphCanvas
 }
+
+/**
+ * Creates a mock LGraph with trigger function
+ */
+export function createMockLGraph(overrides: Partial<LGraph> = {}): LGraph {
+  return {
+    trigger: vi.fn(),
+    ...overrides
+  } as LGraph
+}
+
+/**
+ * Creates a mock CanvasPointerEvent
+ */
+export function createMockCanvasPointerEvent(
+  canvasX: number,
+  canvasY: number,
+  overrides: Partial<CanvasPointerEvent> = {}
+): CanvasPointerEvent {
+  return {
+    canvasX,
+    canvasY,
+    ...overrides
+  } as CanvasPointerEvent
+}
+
+/**
+ * Creates a mock CanvasRenderingContext2D
+ */
+export function createMockCanvasRenderingContext2D(
+  overrides: Partial<CanvasRenderingContext2D> = {}
+): CanvasRenderingContext2D {
+  const partial: Partial<CanvasRenderingContext2D> = {
+    measureText: vi.fn(() => ({ width: 10 }) as TextMetrics),
+    ...overrides
+  }
+  return partial as CanvasRenderingContext2D
+}
+
+/**
+ * Creates a mock LinkNetwork
+ */
+export function createMockLinkNetwork(
+  overrides: Partial<LinkNetwork> = {}
+): LinkNetwork {
+  return {
+    ...overrides
+  } as LinkNetwork
+}
+
+/**
+ * Creates a mock INodeInputSlot
+ */
+export function createMockNodeInputSlot(
+  overrides: Partial<INodeInputSlot> = {}
+): INodeInputSlot {
+  return {
+    ...overrides
+  } as INodeInputSlot
+}
+
+/**
+ * Creates a mock INodeOutputSlot
+ */
+export function createMockNodeOutputSlot(
+  overrides: Partial<INodeOutputSlot> = {}
+): INodeOutputSlot {
+  return {
+    ...overrides
+  } as INodeOutputSlot
+}
+
+/**
+ * Creates a real LGraphNode instance (not a lightweight mock) with its boundingRect
+ * property represented as a Float64Array for testing position methods.
+ *
+ * Use createMockLGraphNodeWithArrayBoundingRect when:
+ * - Tests rely on Float64Array boundingRect behavior
+ * - Tests call position-related methods like updateArea()
+ * - Tests need actual LGraphNode implementation details
+ *
+ * Use createMockLGraphNode when:
+ * - Tests only need simple/mock-only behavior
+ * - Tests don't depend on boundingRect being a Float64Array
+ * - A lightweight mock with minimal properties is sufficient
+ *
+ * @param name - The node name/type to pass to the LGraphNode constructor
+ * @returns A fully constructed LGraphNode instance with Float64Array boundingRect
+ */
+export function createMockLGraphNodeWithArrayBoundingRect(
+  name: string
+): LGraphNode {
+  const node = new LGraphNode(name)
+  // The actual node has a Float64Array boundingRect, we just need to type it correctly
+  return node
+}
+
+/**
+ * Creates a mock FileList from an array of files
+ */
+export function createMockFileList(files: File[]): FileList {
+  const fileList = {
+    ...files,
+    length: files.length,
+    item: (index: number) => files[index] ?? null,
+    [Symbol.iterator]: function* () {
+      yield* files
+    }
+  }
+  return fileList as FileList
+}