feat(bar): expand focused window subwidget

This commit ensures that the focused window komorebi subwidget is aware
of multi-window containers and displays an ordered list of windows in a
container stack which can be clicked to change focus in the stack.

When there are >1 windows in a stack, the title of the focused window
will take from komorebi.json's theme.stack_border if theme is defined
(falling back to the same default value in komorebi), or from
theme.accent in komorebi.bar.json, if defined.

komorebi-bar/src/media.rs

@@ -102,7 +102,8 @@ impl BarWidget for Media {
                     .add(
                         Label::new(layout_job)
                             .selectable(false)
-                            .sense(Sense::click()),
+                            .sense(Sense::click())
+                            .truncate(),
                     )
                     .clicked()
                 {