Non-idempotent with empty line at beginning of file and wrong identation

With defaults, given an empty line plus a wrongly indented item on the next line, e.g. (using non-Rust formatting to avoid the Markdown renderer removing the first empty line):

```

    use a;
```

The first pass gives:

```

use a;
```

The second pass gives:

```
use a;
```

Reproduces with:

```
rustfmt 1.8.0-stable (1159e78c47 2025-09-14)
rustfmt 1.8.0-nightly (be0ade2b60 2025-10-11)
```