```python
def apply_overrides(base: dict, overrides: list) -> dict:
    """Apply command-line overrides to a base configuration dictionary."""
    if not isinstance(overrides, list):
        raise ValueError("overrides must be a list")
    
    merged = dict(base)
    
    for override in overrides:
        if not isinstance(override, str):
            raise ValueError("each override must be a string")
        
        if '=' not in override:
            raise ValueError("override must contain an equals sign")
        
        name, value = override.split('=', 1)
        
        if not name:
            raise ValueError("override name cannot be empty")
        
        if name not in base:
            raise ValueError(f"unknown setting name: {name}")
        
        merged[name] = value
    
    return merged
```