Move failed with filename on windows example čimú

```
var resp = await fetch(url, {
method: "MOVE",
headers: {
destination: newURL
}
})
```

```
Failed to read the 'headers' property from 'RequestInit': String contains non ISO-8859-1 code point.
```

Start from the shown JavaScript fetch call that sends a MOVE request and reproduce it with the filename "čimú" on Windows. Trace how the destination header is created and identify a fix that avoids the ISO-8859-1 error; done means the request accepts the filename successfully.

Written by the indexing model from the issue text.