[Bug]: Preview as Text not showing output in App Mode

### Prerequisites

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

### What happened?

App Mode doesn't display text output, despite the correct node being included in the outputs in the App Builder:

### Steps to Reproduce

1. Import a workflow as simple as Concatenate Text > Preview as Text
2. Enter App mode (Alt + m) then click Build App
4. In Inputs, select at least 1 input from `Concatenate Text` node
6. In Outputs, select the `Preview as Text` node
7. Save, then View app
8. Enter anything, then hit Run

Notice how the workflow runs successfully but there is no output visible.

### Workflow

```json
{"1":{"inputs":{"string_a":"Prefix","string_b":"Suffix","delimiter":" - "},"class_type":"StringConcatenate","_meta":{"title":"Concatenate Text"}},"2":{"inputs":{"source":["1",0]},"class_type":"PreviewAny","_meta":{"title":"Preview as Text"}}}
```

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

1.49.6

### Browser

Chrome/Chromium

### Console Errors

```javascript

```

### Logs

```shell
[INFO] got prompt
[INFO] Prompt executed in 0.02 seconds
```

### Additional Context

## System Info
OS: win32
Python Version: 3.13.14 (tags/v3.13.14:fd17997, Jun 10 2026, 13:03:48) [MSC v.1944 64 bit (AMD64)]
Embedded Python: true
PyTorch Version: 2.13.0+cu130
Arguments: ComfyUI\main.py --windows-standalone-build --disable-all-custom-nodes
RAM Total: 31.36 GB
RAM Free: 16.68 GB
Templates Version: 0.11.44

## Devices
- cuda:0 NVIDIA GeForce RTX 3080 Laptop GPU : cudaMallocAsync (cuda)
VRAM Total: 8 GB
VRAM Free: 6.94 GB
Torch VRAM Total: 0 B
Torch VRAM Free: 0 B

Reproduce the Concatenate Text > Preview as Text workflow in App Mode using the provided JSON, then follow the App Builder output-selection and PreviewAny output-rendering entry points. Compare the successful run with the missing output case; done means the selected Preview as Text output is visible after running the saved app.

Written by the indexing model from the issue text.