Upgrade fails on windows due to access denied

> output of that command is
> ```
> $ uv tool install --upgrade calkit-python
> error: Querying Python at `C:\Users\rgm222\AppData\Roaming\uv\tools\calkit-python\Scripts\python.exe` failed with exit status exit code: 106
>
> [stderr]
> No pyvenv.cfg file
> ```
> both before and after a `uv self update`, which successfully updated from 0.6.12 to 0.9.17.

_Originally posted by @rebeccamccabe in [#635](https://github.com/calkit/calkit/issues/635#issuecomment-3643488396)_

Was able to reproduce this:

```
$ calkit upgrade
Resolved 198 packages in 1.49s
Audited 198 packages in 10ms
error: failed to remove directory `C:\Users\peteb\AppData\Roaming\uv\tools\calkit-python\Scripts`: Access is denied. (os error 5)
Error: Upgrade failed
```

This is probably because Calkit is running at the time of the upgrade, so the Scripts dir can't be replaced.