chore: add @internal JSDoc tag to SubgraphNode.rebuildInputWidgetBindings()

## Follow-up task

Add the `@internal` JSDoc tag to `rebuildInputWidgetBindings()` in `src/lib/litegraph/src/subgraph/SubgraphNode.ts`.

### Context

`rebuildInputWidgetBindings()` is currently public but is only called from `_repointAncestorPromotions` in `LGraph.ts`. Adding `@internal` signals that this method is not part of the stable public API.

**File:** `src/lib/litegraph/src/subgraph/SubgraphNode.ts`

**Change needed:**
```ts
/**
* Clears all cached promoted widget views and re-resolves `input._widget`
* bindings from the current subgraph connections. Called after ancestor
* promotions are repointed during nested subgraph packing.
* @internal
*/
rebuildInputWidgetBindings(): void {
```

### References
- PR: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10532
- Review comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10532#discussion_r2992018036

/cc @christian-byrne

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-10554-chore-add-internal-JSDoc-tag-to-SubgraphNode-rebuildInputWidgetBindings-32f6d73d365081e98361cdcd7fd2e360) by [Unito](https://www.unito.io)