`%date:yyyy-MM-dd%` doesn't work when passed in from an external PrimitiveString

### Custom Node Testing

- [ ] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

The %% field is replaced with the correct string before being passed to the filesystem parser.

### Actual Behavior

Fails with the error:

File "Q:\StableDiffusion\ComfyUI_windows_portable\ComfyUI\folder_paths.py", line 404, in get_save_image_path
os.makedirs(full_output_folder, exist_ok=True)
File "", line 225, in makedirs
NotADirectoryError: [WinError 267] The directory name is invalid: 'Q:\\StableDiffusion\\ComfyUI_windows_portable\\ComfyUI\\output\\WanVideo_Output-%date:yyyy-MM-dd%'

### Steps to Reproduce

Copied the exact text from the filename_prefix field into a PrimitiveString node, and it fails with the error.

### Debug Logs

```powershell
File "Q:\StableDiffusion\ComfyUI_windows_portable\ComfyUI\folder_paths.py", line 404, in get_save_image_path
os.makedirs(full_output_folder, exist_ok=True)
File "", line 225, in makedirs
NotADirectoryError: [WinError 267] The directory name is invalid: 'Q:\\StableDiffusion\\ComfyUI_windows_portable\\ComfyUI\\output\\WanVideo_Output-%date:yyyy-MM-dd%'
```

### Other

_No response_