feature request: insert into multiple windows

In a layout like the screenshot, if I want window 2 to span the top of the screen, there's no easy way to get there and it's even harder if there more windows on the screen as they shift around. Ideally we could do something like:
```
yabai -m window 2 --toggle float
yabai -m window 1 --insert north
yabai -m window 3 --insert north
yabai -m window 2 --toggle float
```

Thanks!

Start by tracing the `yabai -m window` command handling for `--toggle float` and `--insert`, using the requested sequence as the behavioral example. Done means window 2 can span the top of the screen while additional windows do not shift unpredictably, with the command sequence producing the intended layout.

Written by the indexing model from the issue text.