Improve the `everyvoice check-data` help

### Bug description

`everyvoice -h` includes this:
```
## Check Data

You can optionally check your data by running everyvoice check-data [OPTIONS]
```

But the command is declared as hidden
```
@app.command(hidden=True)
def check_data(
```

and the help is not really sufficient to know what to do with it:
```
$ everyvoice check-data -h

Usage: everyvoice check-data [OPTIONS] CONFIG_FILE

╭─ Arguments ─────────────────────────────────────────────────────────────╮
│ * config_file FILE The path to your model configuration file. │
│ [default: None] │
│ [required] │
╰─────────────────────────────────────────────────────────────────────────╯
```

The help should answer:
- Of the six config files in `config/` generated by the wizard, which ones are OK to use here?
- what gets checked?

By trial and error, this command seems to accept `config/everyvoice-aligner.yaml` and `config/everyvoice-text-to-spec.yaml` but the code seems to suggest three types of models are accepted, so we need more clarity.

Related issue, the error messages you get when you choose the wrong type of config file could be improved by listing what models this CLI command accepts in that error message. It is already going in that direction, but it's not clear enough. In particular, "Please pass a valid EveryVoice model or shared data configuration file." is misleading because `config/everyvoice-shared-data.yaml` tells me "Sorry, your file does not appear to be a valid model configuration.".

### How to reproduce the bug

_No response_

### Error messages and logs

```
# Error messages and logs here please
```

### Environment

Current environment

```
#- EveryVoice Version:
#- PyTorch Lightning Version (e.g., 2.4.0):
#- PyTorch Version (e.g., 2.4):
#- Python version (e.g., 3.12):
#- OS (e.g., Linux):
#- CUDA/cuDNN version:
#- GPU models and configuration:
#- How you installed EveryVoice (`conda`, `pip`, source):
```

### More info

_No response_