Inconsistent chart lengths

The chart lengths are inconsistent within each hour when I run `timew day`. They are more compressed at the beginning of the hour than at the end.

Here I've set up two hours of tracking with a one hour, half hour, and two 15 minute chunks.

```
timew summary :ids
```


```
timew day rc.reports.day.spacing=7 rc.reports.day.hours=auto rc.reports.day.axis=external
```

I'm running this in the kitty terminal and timew `1.4.3` installed via homebrew.

Thanks!