README utilization example uses --processes, but the command defines --workers

Noted while adding the *Queues* section to the README (fair multi-queue scheduling, `codingjoe-fair-multi-queue-scheduling`).

The README's *Utilization* section advertises:

```console
uv run manage.py threadmill worker --processes 4 --threads 2
```

but `WorkerCommand.add_arguments()` defines `-w`/`--workers`, not `--processes`. The example fails with an unrecognised-argument error.

Fix is to rename the flag in the README example (or add an alias, if `--processes` is the intended name).

打开 README 的 Utilization 部分，将其中的 worker 命令示例与定义可用 flags 的 WorkerCommand.add_arguments() 进行比较。更新示例，使其使用预期的选项，然后验证文档中的命令不再产生 unrecognised-argument 错误。

由索引模型根据 Issue 内容生成。