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/extensions/core/nodeTemplates.ts

@@ -370,9 +370,10 @@ const ext: ComfyExtension = {
             const node = app.canvas.graph?.getNodeById(nodeIds[i])
             const nodeData = node?.constructor.nodeData
 
-            let groupData = GroupNodeHandler.getGroupData(node)
-            if (groupData) {
-              groupData = groupData.nodeData
+            if (!node) continue
+            const groupConfig = GroupNodeHandler.getGroupData(node)
+            if (groupConfig) {
+              const groupData = groupConfig.nodeData
               // @ts-expect-error
               if (!data.groupNodes) {
                 // @ts-expect-error
@@ -402,7 +403,10 @@ const ext: ComfyExtension = {
         callback: () => {
           clipboardAction(async () => {
             const data = JSON.parse(t.data)
-            await GroupNodeConfig.registerFromWorkflow(data.groupNodes, {})
+            await GroupNodeConfig.registerFromWorkflow(
+              data.groupNodes ?? {},
+              []
+            )
 
             // Check for old clipboard format
             if (!data.reroutes) {