Unify window presentation and frame-driven shell motion

Share window geometry across overview, resize snapshots and retained closes. Advance close handoffs and group retained rendering by stacking position.

Drive shell motion from surface frames, reuse settled widget content, and synchronize notification materials with each card's fade. Replace physical config keys with duration and bounce, and update documentation and regression coverage.

shell/ferese-shell/src/system_modal.rs

@@ -468,7 +468,32 @@ impl FereseShell {
         let Some(surface) = modal.surfaces.iter().find(|surface| surface.id == id) else {
             return text("").into();
         };
-        let progress = modal.motion.progress();
+        motion::frame_driven(
+            modal.motion.revision(),
+            move |now| self.view_system_modal_at(id, now),
+            |now| modal.motion.frame_active(now),
+            |now| {
+                if let Some(effects) = &surface.effects {
+                    let _ = effects
+                        .set_material_regions(&surface.regions.lock().unwrap(), ferese_surface_effects_v1::Role::Modal);
+                    let _ = effects.set_opacity(modal.motion.progress_at(now).clamp(0.0, 1.0));
+                }
+            },
+            |now| {
+                (surface.primary && modal.motion.closing() && !modal.motion.animating_at(now))
+                    .then_some(cosmic::Action::App(Message::AnimatePower))
+            },
+        )
+    }
+
+    fn view_system_modal_at(&self, id: window::Id, now: Instant) -> Element<'_, cosmic::Action<Message>> {
+        let Some(modal) = &self.system_modal else {
+            return text("").into();
+        };
+        let Some(surface) = modal.surfaces.iter().find(|surface| surface.id == id) else {
+            return text("").into();
+        };
+        let progress = modal.motion.progress_at(now);
         let content: Element<'_, cosmic::Action<Message>> = if surface.primary {
             let theme = self.config.theme;
             let material = surface.effects.is_some();