Nodes 2.0: Combo/dropdown widgets missing previous/next stepper arrows (impacts Load Image browsing)

### Prerequisites

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

### What happened?

### Prerequisites
- I am running the latest version of ComfyUI
- I have searched existing issues to make sure this isn't a duplicate
- I have tested with all custom nodes disabled

### What happened?

In legacy (LiteGraph) node rendering, combo/dropdown widgets have small ← → arrow buttons that let you step through options one at a time without opening the full dropdown. This is especially useful on the **Load Image** node, where you may have dozens or hundreds of images in the input folder and want to quickly cycle through them.

In **Nodes 2.0**, these stepper arrows are missing from combo widgets. The only way to change the selected image is to open the full dropdown list and scroll/search, which is significantly slower for browsing.

Note: The Primitive node's pencil icon for "control before generate" (increment/decrement) **does work** in Nodes 2.0, so you can set up auto-cycling per generation. But this doesn't replace the need for manual prev/next navigation on the node itself — for example, when you want to visually browse through your input images to find the right one before running.

Integer widgets in Nodes 2.0 do have +/- stepper buttons, so the pattern already exists in the new Vue widget system — it just wasn't carried over to combo widgets.

### Expected Behavior

Combo/dropdown widgets in Nodes 2.0 should have previous/next stepper arrows (or equivalent UI) matching the legacy LiteGraph behavior, allowing users to step through options one at a time without opening the dropdown.

### Actual Behavior

Combo widgets only show a dropdown selector with no stepper controls. The only way to change selection is opening the full dropdown.

### How is this affecting you?

Makes browsing input images significantly slower and less ergonomic. This is a workflow regression from legacy nodes.

### Related Issues

- #11384 — Missing "control after generate" dropdown in Nodes 2.0 (related Nodes 2.0 widget parity gap)
- Comfy-Org/ComfyUI#12945 — Discussion on control-after-generate UX in Nodes 2.0

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### Steps to Reproduce

1. Enable Nodes 2.0
2. Add a **Load Image** node
3. Observe that the image selector dropdown has no ← → arrows to step through images
4. Disable Nodes 2.0 and observe the arrows reappearing on the same widget

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

ComfyUI 0.22.0, ComfyUI_frontend v1.43.18

### Browser

Chrome/Chromium

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

(That's the 'with subfolder' node, but it's exactly the same issue with the normal node. Although there's also a bug with `` not actually properly showing images that exist in subfolders inside the input folder, even though the loading of the image works fine, and it does preview it in the box and has forever)