```python
def apply_overrides(base: dict, overrides: list) -> dict:
    """Apply command-line overrides to the base settings."""
    if not isinstance(overrides, list):
        raise ValueError("Overrides must be a list.")
    
    merged = base.copy()
    for override in overrides:
        if not isinstance(override, str):
            raise ValueError("Each override must be a string.")
        
        equals_index = override.find('=')
        if equals_index == -1:
            raise ValueError("Override must contain an equals sign.")
        if equals_index == 0:
            raise ValueError("Override name cannot be empty.")
        
        name = override[:equals_index]
        if name not in base:
            raise ValueError(f"Override name '{name}' not found in base settings.")
        
        value = override[equals_index + 1:]
        merged[name] = value
    
    return merged
```