--show-external-plugins won't

### Bug

docling (main latest) won't show external plugins.

`docling --show-external-plugins` outputs `The plugin lazarus_gemma_vlm will not be loaded because Docling is being executed with allow_external_plugins=false`

### Steps to reproduce
- implement a plugin

```
# src/lazarus_docling_plugin/vlm.py
MODEL_CLI_NAME = "gemma_3_4b_lazarus"
MODEL_HF_REPO = "mlx-community/gemma-3-4b-it-8bit"

def docling_register():
gemma_vlm_config = HuggingFaceVlmOptions(
inference_framework="mlx",
model_name_or_path=MODEL_HF_REPO,
response_format="doctags"
)
return {
"vlm_options": {
MODEL_CLI_NAME: gemma_vlm_config
}
}
```

```
# src/lazarus_docling_plugin/__init__.py

```

```
# pyproject.toml
[build-system]
requires = ["setuptools>=61.0"]
build-backend = "setuptools.build_meta"

[project]
name = "lazarus-docling-plugin"
version = "0.1.0"
description = "Docling plugin to register the MLX Gemma 3 4B IT model."
requires-python = ">=3.8"
dependencies = [
"docling>=1.0.0",
]

[project.entry-points."docling"]
lazarus_gemma_vlm = "lazarus_docling_plugin.vlm"

```

- `python -m build`
- `pip install --force-reinstall dist/lazarus_docling_plugin-*.whl`
- `docling --show-external-plugins`

Expected:

my plugin is listed

Observed:

```
The plugin lazarus_gemma_vlm will not be loaded because Docling is being executed with allow_external_plugins=false.
```

### Docling version
```
The plugin lazarus_gemma_vlm will not be loaded because Docling is being executed with allow_external_plugins=false.
Docling version: 2.30.0
Docling Core version: 2.28.0
Docling IBM Models version: 3.4.2
Docling Parse version: 4.0.1
Python: cpython-312 (3.12.2)
Platform: macOS-15.4.1-arm64-arm-64bit
```

### Python version
```
Python 3.12.2
```