fix: improve type safety in litegraph library layer - No Explicit Any mission (PR 2) (#7401)

## Summary

Part 2 of the type safety remediation plan. This PR focuses on the
Litegraph Library Layer as part of the **No Explicit Any** mission.

### Changes

**LiteGraphGlobal.ts:**
- `DEFAULT_GROUP_FONT_SIZE`: Changed from `any` (with no value) to
`number = 24`. The internal fallback was already 24, so the constant was
effectively useless without an assigned value.
- `getParameterNames`: Replace `any` with `unknown` in function
signature
- `extendClass`: Replace deprecated
`__lookupGetter__`/`__defineGetter__` with modern
`Object.getOwnPropertyDescriptor`/`defineProperty` and add proper Record
types

**LGraphNodeProperties.ts:**
- Replace `any` with `unknown` for property values
- Use `Record<string, unknown>` with proper type assertions for dynamic
property access

**types/widgets.ts & BaseWidget.ts:**
- Change `callback` value parameter from `any` to properly typed
(`unknown` in interface, `TWidget['value']` in implementation)

**Consuming code fixes:**
- `previewAny.ts`: Add explicit `boolean` type annotation for callback
value
- `ButtonWidget.ts`: Pass widget value instead of widget instance to
callback (matching the interface signature)

## Breaking Change Analysis (Sourcegraph Verified)

### ButtonWidget callback fix (`this` → `this.value`)
This PR fixes the ButtonWidget callback to pass `value` instead of
`this`, matching the interface definition.

**Verification via Sourcegraph** - all external usages are safe:
-
[comfyui-ollama](https://cs.comfy.org/github.com/stavsap/comfyui-ollama/-/blob/web/js/OllamaNode.js?L84)
- doesn't use callback args
-
[ComfyLab-Pack](https://cs.comfy.org/github.com/bugltd/ComfyLab-Pack/-/blob/dist/js/nodes/list.js?L8)
- doesn't use callback args
-
[ComfyUI_PaintingCoderUtils](https://cs.comfy.org/github.com/jammyfu/ComfyUI_PaintingCoderUtils/-/blob/web/js/click_popup.js?L18)
- doesn't use callback args
-
[ComfyUI-ShaderNoiseKSampler](https://cs.comfy.org/github.com/AEmotionStudio/ComfyUI-ShaderNoiseKSampler/-/blob/web/matrix_button.js?L3055-3056)
- was already working around this bug

---------

Co-authored-by: GitHub Action <action@github.com>

src/extensions/core/previewAny.ts

@@ -41,7 +41,7 @@ useExtensionService().registerExtension({
           app
         )
 
-        showAsPlaintextWidget.widget.callback = (value) => {
+        showAsPlaintextWidget.widget.callback = (value: boolean) => {
           showValueWidget.hidden = !value
           showValueWidget.options.hidden = !value
           showValueWidgetPlain.hidden = value