```python
def case_count(text: str) -> list:
    if not text:
        return [0, 0]

    caps = sum(1 for char in text if char.isupper())
    lows = sum(1 for char in text if char.islower())

    return [caps, lows]
```

This solution implements the `case_count` function as specified in the task contract. It correctly counts the number of capital letters and small letters in the input string, with zero-counted non-letter characters. The function returns a list containing the counts of capitals followed by the counts of lowercase letters.