Function sync_tab_selected 

pub fn sync_tab_selected(
    commands: Commands<'_, '_>,
    store: Res<'_, PropertyStore>,
    buttons: Query<'_, '_, (Entity, &TabStripButton, Option<&Selected>)>,
)

Maintain the Selected marker across every tab strip: the button whose value matches its bound signal’s current value carries it; all its siblings shed it. Idempotent per tick - insert / remove only fire on actual transitions, so archetypes stay put on idle frames.