perf(props): skip focus sweep when the properties panel is hidden

The global left-click listener fires PropPointerPressed on every mouse
press anywhere in the app, and the handler used to launch a full
widget-tree focus sweep on each one - even when the Properties panel
was closed. Gate the sweep on dock_panel_visible(Properties): when the
panel is hidden the handler now returns Task::none, turning an O(whole
UI) traversal per click into an O(1) boolean check in the common case.

The other sweep call sites already gate via sync_active_field_if_any;
this was the only ungated one.

Tests:
- hidden_properties_panel_skips_the_focus_sweep - a click with the
  panel closed returns a Task::none (units == 0), i.e. no sweep.
- visible_properties_panel_runs_the_focus_sweep - a click with the
  panel open still fires the sweep (units > 0), preserving the
  select-whole-value behavior.

src/app/update/mod.rs

@@ -4633,7 +4633,7 @@ impl OpenCADStudio {
             Message::PropAttrCommit(tag) => self.on_prop_attr_commit(tag),
 
             Message::PropPointerPressed => {
-                if self.tabs[self.active_tab].is_start || self.clean_screen {
+                if !self.dock_panel_visible(crate::ui::dock::PanelId::Properties) {
                     return Task::none();
                 }
                 crate::ui::properties::sync_active_field_task()
@@ -7531,3 +7531,41 @@ impl OpenCADStudio {
         }
     }
 }
+
+#[cfg(test)]
+mod prop_pointer_tests {
+    use super::Message;
+    use crate::app::OpenCADStudio;
+    use crate::ui::dock::PanelId;
+
+    fn drawing_app() -> OpenCADStudio {
+        let mut app = OpenCADStudio::new_for_test();
+        app.automation_op(r#"{"op":"new"}"#);
+        app
+    }
+
+    #[test]
+    fn hidden_properties_panel_skips_the_focus_sweep() {
+        // A click while the panel is closed must not run the widget-tree sweep:
+        // the returned task is a bare `Task::none` (units == 0).
+        let mut app = drawing_app();
+        assert!(app.dock_panel_visible(PanelId::Properties));
+        app.show_properties = false;
+        assert!(!app.dock_panel_visible(PanelId::Properties));
+
+        let task = app.update(Message::PropPointerPressed);
+        assert_eq!(task.units(), 0);
+    }
+
+    #[test]
+    fn visible_properties_panel_runs_the_focus_sweep() {
+        // A click while the panel is open must still fire the sweep (units > 0)
+        // so the select-whole-value feature keeps working.
+        let mut app = drawing_app();
+        app.show_properties = true;
+        assert!(app.dock_panel_visible(PanelId::Properties));
+
+        let task = app.update(Message::PropPointerPressed);
+        assert!(task.units() > 0);
+    }
+}