global --format after a subcommand fails with an unhelpful clap error

## Repro (stock CLI v0.5.2)

`buzz --help` documents global `--format json|compact`.

This works:

```
buzz --format json messages get --channel --limit 1
```

This fails:

```
buzz messages get --format json --channel --limit 1
```

Error:

```
error: unexpected argument '--format' found
Usage: buzz messages get [OPTIONS] --channel
```

The failure is wrapped as JSON `user_error` and still exits 0.

## Expected

Either accept `--format` after the subcommand, or say it is a global flag that must precede the subcommand (and exit nonzero).