```python
def line_up(links: dict[str, str], start: str) -> list[str]:
    if start not in links:
        raise ValueError("Unknown name")
    
    line = [start]
    current = start
    
    while True:
        next_name = links.get(current)
        if next_name is None:
            break
        if next_name in line:
            raise ValueError("Circular link detected")
        line.append(next_name)
        current = next_name
    
    return line
```