Using `sub-layer` leaves top of stack always on top

I'm using `yabai -m rule --add app=".*" sub-layer=normal` to enable managed windows to appear in front of unmanaged windows, as detailed [here](https://github.com/koekeishiya/yabai/issues/1929).

However, my observation is that with this setting, when windows are stacked, switching the focus to windows deeper in the stack does not bring them to the top; instead whatever is on top remains the visible window, effectively rendering stacks useless.

Is this intended behavior? Is it possible to use stacks and have unamanged windows not always appear on top without manipulating the sub-layers of individual windows?

Reproduce the exact `yabai -m rule --add app=".*" sub-layer=normal` setup with managed and unmanaged stacked windows, then focus a deeper window. No source file or test is named in the report, so trace the stack-focus and sub-layer entry points from that behavior. Done means determining whether the focused stacked window becomes visible while unmanaged windows remain below, and adding a regression check if the behavior is a bug.

Written by the indexing model from the issue text.