fix: replace as-unknown-as casts with safer patterns (#9107)

## Summary

- Replace 83 `as unknown as` double casts with safer alternatives across
33 files
- Use `as Partial<X> as X` pattern where TypeScript allows it
- Create/reuse factory functions from `litegraphTestUtils.ts` for mock
objects
- Widen `getWorkflowDataFromFile` return type to include `ComfyMetadata`
directly
- Reduce total `as unknown as` count from ~153 to 71

The remaining 71 occurrences are genuinely necessary due to cross-schema
casts, generic variance, missing index signatures, Float64Array-to-tuple
conversions, and DOM type incompatibilities.

## Test plan

- [x] `pnpm typecheck` passes
- [x] `pnpm lint` passes
- [x] All affected unit tests pass

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9107-fix-replace-as-unknown-as-casts-with-safer-patterns-3106d73d3650815cb5bcd613ad635bd7)
by [Unito](https://www.unito.io)

src/renderer/extensions/vueNodes/composables/useNodeEventHandlers.test.ts

@@ -4,11 +4,7 @@ import { computed, shallowRef } from 'vue'
 import { useGraphNodeManager } from '@/composables/graph/useGraphNodeManager'
 import type { GraphNodeManager } from '@/composables/graph/useGraphNodeManager'
 import { useVueNodeLifecycle } from '@/composables/graph/useVueNodeLifecycle'
-import type {
-  LGraph,
-  LGraphCanvas,
-  LGraphNode
-} from '@/lib/litegraph/src/litegraph'
+import type { LGraphCanvas, LGraphNode } from '@/lib/litegraph/src/litegraph'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { useLayoutMutations } from '@/renderer/core/layout/operations/layoutMutations'
 import { useNodeEventHandlers } from '@/renderer/extensions/vueNodes/composables/useNodeEventHandlers'
@@ -64,7 +60,7 @@ vi.mock('@/composables/graph/useGraphNodeManager', () => {
 })
 
 vi.mock('@/composables/graph/useVueNodeLifecycle', () => {
-  const nodeManager = useGraphNodeManager(undefined as unknown as LGraph)
+  const nodeManager = useGraphNodeManager(null!)
   return {
     useVueNodeLifecycle: vi.fn(() => ({
       nodeManager

src/renderer/extensions/vueNodes/interactions/resize/useNodeResize.test.ts

@@ -108,7 +108,7 @@ function createPointerEvent(
     preventDefault: vi.fn(),
     stopPropagation: vi.fn(),
     ...overrides
-  } as unknown as PointerEvent
+  } as Partial<PointerEvent> as PointerEvent
 }
 
 function startResizeAt(