Chore: TypeScript cleanup - remove 254 @ts-expect-error suppressions (#7884)

## Summary

Removes **254** `@ts-expect-error` suppressions through proper type
fixes rather than type assertions.

## Key Changes

### Type System Improvements
- Add `globalDefs` and `groupNodes` types to `ComfyAppWindowExtension`
- Extract interfaces for group node handling (`GroupNodeHandler`,
`InnerNodeOutput`, etc.)
- Add `getHandler()` helper to consolidate GROUP symbol access pattern

### Files Fixed
- **pnginfo.ts**: 39 suppressions removed via proper typing of
workflow/prompt data
- **app.ts**: 39 suppressions removed via interface extraction and type
narrowing
- **Tier 1 files**: 17 suppressions removed (maskeditor, imageDrawer,
groupNode, etc.)
- **groupNode.ts**: Major refactoring with proper interface organization

## Approach

Following established constraints:
- No `any` types
- No `as unknown as T` casts (except legacy API boundaries)
- Priority: Fix actual types > Type narrowing > Targeted suppressions as
last resort
- Prefix unused callback parameters with underscore
- Extract repeated inline types into named interfaces

## Validation

- ✅ `pnpm typecheck` passes
- ✅ `pnpm lint` passes
- ✅ `pnpm knip` passes

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7884-Chore-TypeScript-cleanup-remove-254-ts-expect-error-suppressions-2e26d73d3650812e9b48da203ce1d296)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

src/lib/litegraph/src/LGraph.ts

@@ -15,7 +15,7 @@ import { LGraphGroup } from './LGraphGroup'
 import { LGraphNode } from './LGraphNode'
 import type { NodeId } from './LGraphNode'
 import { LLink } from './LLink'
-import type { LinkId } from './LLink'
+import type { LinkId, SerialisedLLinkArray } from './LLink'
 import { MapProxyHandler } from './MapProxyHandler'
 import { Reroute } from './Reroute'
 import type { RerouteId } from './Reroute'
@@ -102,11 +102,24 @@ export interface LGraphConfig {
   links_ontop?: any
 }
 
+export interface GroupNodeWorkflowData {
+  external: (number | string)[][]
+  links: SerialisedLLinkArray[]
+  nodes: {
+    index?: number
+    type?: string
+    inputs?: unknown[]
+    outputs?: unknown[]
+  }[]
+  config?: Record<number, unknown>
+}
+
 export interface LGraphExtra extends Dictionary<unknown> {
   reroutes?: SerialisableReroute[]
   linkExtensions?: { id: number; parentId: number | undefined }[]
   ds?: DragAndScaleState
   workflowRendererVersion?: RendererType
+  groupNodes?: Record<string, GroupNodeWorkflowData>
 }
 
 export interface BaseLGraph {