"""Calculates the temporal balance between recent and evergreen components.

This function determines the balance between recent and evergreen components based on their ratio. The balance is categorized into three types: 'recent_heavy', 'evergreen_heavy', or 'balanced'. If both components sum to zero, the balance is considered 'unknown'.

Args:
    recent (int): The count of recent components.
    evergreen (int): The count of evergreen components.

Returns:
    str: A string indicating the balance type. Possible values are:
        - 'recent_heavy': If the ratio of recent components to total is greater than 0.7.
        - 'evergreen_heavy': If the ratio of recent components to total is less than 0.3.
        - 'balanced': If the ratio of recent components to total is between 0.3 and 0.7.
        - 'unknown': If the total count of components is zero.
"""