Backend-populated combo widgets (checkpoint, sampler, scheduler) won't open or respond to arrows; numeric/text widgets work

### Prerequisites

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

### What happened?

COMBO widgets whose options come from the backend (ckpt_name on CheckpointLoaderSimple, sampler_name and scheduler on KSampler) do not respond to clicks. The dropdown list won't open, and the ◄ ► arrows do nothing, so the value can't be changed at all. Numeric and text widgets on the same nodes (seed, steps, cfg, denoise, control_after_generate, CLIP Text Encode textarea) work normally. Node right-click menu, selection toolbox, sidebar, tabs, and Run all work. No errors in the browser console on click. /object_info returns full JSON including the sampler/scheduler/checkpoint lists, so the option data reaches the frontend — the widget just won't open or cycle.

### Steps to Reproduce

1. Fresh official Windows portable install, launched with --front-end-version Comfy-Org/ComfyUI_frontend@1.46.9
2. Add a KSampler node
3. Click the sampler_name combo widget, or click its ◄ ► arrows
4. Nothing happens — list won't open, value won't change. Same for scheduler and for ckpt_name on Load Checkpoint.

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

1.46.9

### Browser

Edge

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

Tested and reproduces on frontend 1.47.2 (nightly), 1.45.18, and 1.46.9 — including the build with #12211 "Fix restoring values to dynamic combos".
Tested on Edge (normal + incognito) and DuckDuckGo (Chromium) — reproduces on all.

Ruled out: browser cache/incognito, two clean portable reinstalls, custom nodes (only websocket_image_save loads), Windows scaling at 100%, browser zoom reset, hardware acceleration toggle, Nodes 2.0 "Modern Node Design" off, Auto-scale layout toggled, Left Mouse Click Behavior set to Select, node not pinned.

Environment: ComfyUI 0.25.1 official portable, comfy-aimdo 0.4.10, comfy-kitchen 0.2.10, embedded Python 3.13.12, PyTorch 2.12.0+cu130, RTX 5070 12GB driver 591.86, Windows.

Reproduce the issue with KSampler's sampler_name and scheduler and Load Checkpoint's ckpt_name, then trace frontend combo-widget handling for options returned by /object_info. Verify that dropdown clicks and ◄ ► arrows change backend-populated values while numeric and text widgets continue working.

Written by the indexing model from the issue text.