V3 schema: cannot create paired autogrow inputs (image_i + state_i)

### What problem are you experiencing?

I am implementing a node that needs **paired dynamic inputs**, for example:

```
image_1
state_1
image_2
state_2
image_3
state_3
...
```

Desired behavior:

* `image_1` and `state_1` are visible initially
* when `image_1` is connected → `image_2` and `state_2` appear
* when `image_2` is connected → `image_3` and `state_3` appear

However with the current V3 schema system this does not seem possible.

https://github.com/user-attachments/assets/34c95b96-d37f-455b-b87e-884f6bb45059

* `Autogrow` only grows a **single input type**
* there is no way to grow **multiple inputs as a pair**
* frontend `node.addInput()` does not work because schema re-application resets the inputs

As a result, nodes that need per-image metadata/state cannot implement a clean UX.

Is there a recommended way to implement **paired autogrow inputs**, or would support for something like this be considered?

### When does this problem occur?

During custom node development when implementing nodes that require paired dynamic inputs (e.g., an image and its associated state/metadata).

### How often do you encounter this problem?

Daily

### How much does this problem affect your workflow?

Minor annoyance

### Current workarounds

_No response_

### Ideas for solutions (Optional)

_No response_

### Additional context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-9363-V3-schema-cannot-create-paired-autogrow-inputs-image_i-state_i-3196d73d365081a3a5e8e55df3592609) by [Unito](https://www.unito.io)

Start by reproducing the V3 schema behavior with Autogrow and the frontend node.addInput() workaround described in the issue. Trace how schema re-application handles dynamically added inputs, then define completion as paired image_i and state_i inputs appearing sequentially when the preceding pair is connected and remaining intact after schema updates.

Written by the indexing model from the issue text.