Removes stack tracking locally and on GitHub. With no stack number, it targets
the active stack. `--local` preserves the GitHub stack.
Usage:
```bash
quinjet stack unstack [<stack>] [--local] [--yes]
```
Without `--yes`, Quinjet prints a preview and changes nothing.
```bash
quinjet stack unstack 7 --local --yes
```
See [`quinjet stack`](./README.md) for lifecycle safety and prerequisites.