`uv --offline self update` ignores --offline flag.

### Summary

`uv --offline self update` ignores `--offline` flag.

```
$ uv --offline self update
info: Checking for updates...
success: You're on the latest version of uv (v0.7.6)
```

`--offline` is a "Global option" and therefore it should make `uv self update` fail.

### Platform

Linux 6.8.0-60-generic x86_64 GNU/Linux

### Version

uv 0.7.6

### Python version

Python 3.13.2