Labeling windows

I checked the documentation thoroughly and it seems there is no support for labeling windows.
I.e. I'd expect sth like: `yabai -m window [] --label LABEL`.

This would be useful to quickly tag certain windows of interest directly from within yabai, w/o messing with the title.

Any thoughts or alternatives on this?

Start by reviewing the existing `yabai -m window ` command entry point and how window properties are exposed. Define how labels should be represented and managed, then confirm that the proposed command can tag and retrieve selected windows without relying on their titles.

Written by the indexing model from the issue text.