float-ratio-float returns 0 for numbers close to least-positive-float
## Describe the bug
`kernel::float-ratio-float` returns zero (when underflows are
disabled) for numbers that are just less least-positive float. I
think the it should return the least-positive float value instead
because it's closer than 0.
## To Reproduce
Steps to reproduce the behavior:
1. Evaluate `(kernel::float-ratio-float (/ 4 (expt 10 324)) 'double-float)`
2. This returns 0d0
## Expected behavior
I was kind of expecting $4\times 10^{-324}$ to be returned because
that is closer to `least-positive-double-float`
(4.9406564584124654d-324) than it is to 0.
We have the same issue with `single-float`'s and `double-double-float`'s.
## Desktop (please complete the following information):
- OS: All
- Version: snapshot-2023-08
## Additional context
Add any other context about the problem here.
issue