Count Values with an Even Number of Digits

Question

Given a list of positive integers, return how many contain an even number of decimal digits.

```python
def count_even_digit_numbers(numbers: list[int]) -> int: ...
```

For example, `[12, 345, 2, 6, 7896]` returns `2`. Assume every value is positive and fits in a signed 32-bit integer. Target `O(n)` time.

## Staged follow-ups

1. Extend the definition to include zero and negative integers without counting a sign.
2. Avoid converting numbers to strings.
3. Count digits in an arbitrary base supplied at runtime.