Broken ordinal cases

Currently, there are two cases that are uncovered by the tests and produce potentially surprising results:

## float that's also an integer

```python
>>> ordinal(1.0)
'1.0st'
```

That's surprising because other float values produce the suffix based on the last digit of the float (e.g. "1.0th").

## float with no decimal digits

```python
>>> ordinal('1.')
'1.st'
```

Does "1.st" even make sense? The code does attempt to support this case, but I'm not at all confident it should.

Start at the ordinal() entry point and inspect the existing handling for float inputs and strings ending in a decimal point. Add focused tests for the two examples in the issue, then confirm the expected suffix behavior with the project’s test suite once the intended results for both cases are decided.

Written by the indexing model from the issue text.