feat: add reversible workspace panels

spikes/floem-shell/src/main.rs

@@ -346,7 +346,7 @@ fn handle_key(
 }
 
 fn app_view() -> impl IntoView {
-    let model = RwSignal::new(ShellModel::default());
+    let model = RwSignal::new(ShellModel::with_all_panels_attached());
     let query = RwSignal::new(String::new());
     let timer_pulse = RwSignal::new(());