...ns Script (oberhalb von `main()`):

```python
def quote_is_from_assistant(quote: str) -> bool:
    q = (quote or "").lstrip()
    return q.startswith("[ASSISTANT")
```

Und erweitere `validate_schema(...)` um diese Checks:

```python
    # Keine Assistant-Quotes in Markern
    for i, it in enumerate(data["progress_markers"]):
        if quote_is_from_assistant(it["quote"]):
            raise ValueErr...