Subgraph socket connection missing visual feedback

### Prerequisites

- [x] I am running the latest version of ComfyUI
- [x] I have custom nodes enabled

### What happened?

In nodes 2.0 -theres no visual feedback if sockets are going to connect, in subgraphs, with IO

https://github.com/user-attachments/assets/e2f6d65f-59ed-45ce-aeb8-3036e8ffb787

### Steps to Reproduce

1.yes
2.
3.

### How is this affecting you?

Visual/UI issue only

### ComfyUI Frontend Version

1.40.8

### Browser

Chrome/Chromium

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-9010-Subgraph-socket-connection-missing-visual-feedback-30d6d73d36508194b7a6cfc86fba197e) by [Unito](https://www.unito.io)

Start by reproducing the issue in Nodes 2.0 with a subgraph and IO sockets in Chrome/Chromium, using the attached recording as the visual reference. Trace the socket-connection interaction from the frontend entry point you identify; done means connection intent has visible feedback when linking subgraph sockets.

Written by the indexing model from the issue text.