Create `--root` directory when missing

With Chisel 1.3.0 and earlier, the `--root` directory must exist before running chisel.

Could chisel support creating this directory implicitly if it's missing, or provide an opt-in flag to do so if there's a reason not to support this convenience by default?

```bash
chisel cut --release ubuntu-24.04 --root /root-fs base-files_base
```

> ```
> 2025/03/13 02:45:57 Extracting files from package "base-files"...
> error: cannot extract from package "base-files": target directory does not exist
> ```

---

Related to this error is the timing. `chisel` does not bail early, instead doing quite a bit of work prior to failing. This check should occur much earlier before other operations like network activity?

Start by locating the chisel cut command's --root handling and the validation that produces "target directory does not exist"; reproduce the example with a missing /root-fs directory. Done means the intended missing-directory behavior is implemented and validation happens before network activity or extraction work.

Written by the indexing model from the issue text.