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/components/searchbox/v2/NodeSearchInput.test.ts

@@ -31,7 +31,10 @@ function createFilter(
     filterDef: {
       id,
       matches: vi.fn(() => true)
-    } as unknown as FuseFilter<ComfyNodeDefImpl, string>,
+    } as Partial<FuseFilter<ComfyNodeDefImpl, string>> as FuseFilter<
+      ComfyNodeDefImpl,
+      string
+    >,
     value
   }
 }
@@ -43,7 +46,10 @@ function createActiveFilter(label: string): FilterChip {
     filter: {
       id: label.toLowerCase(),
       matches: vi.fn(() => true)
-    } as unknown as FuseFilter<ComfyNodeDefImpl, string>
+    } as Partial<FuseFilter<ComfyNodeDefImpl, string>> as FuseFilter<
+      ComfyNodeDefImpl,
+      string
+    >
   }
 }