cannot accept floating point to integer functions

true code:

```janet
(pp nearest-vertex)
(draw-circle-gradient (splice nearest-vertex) 4.0 :lime :red))))
```

```
(264.160827636719 400)
error: bad slot #0, expected 32 bit signed integer, got 264.160827636719
in jaylib/draw-circle-gradient
in _thunk [main.janet] (tailcall) on line 42, column 9
```

## Reproduction

```
(draw-circle-gradient [264.160827636719 400] 4.0 :lime :red)
```

Start at the jaylib/draw-circle-gradient entry point and reproduce the provided call with the floating-point coordinate. Trace how its arguments are validated or converted, then confirm the intended handling for a floating-point value and add or update coverage so the reported error case has a defined result.

Written by the indexing model from the issue text.