feat(properties): refine quick properties

- Keep the floating panel near the selection and inside the viewport
- Persist the toggle and hide the panel without a selection
- Show only Material in 3D Visualization

src/app/mod.rs

@@ -352,6 +352,8 @@ pub(super) struct OpenCADStudio {
     clean_screen: bool,
     /// Quick Properties: show a compact floating property panel on selection.
     quick_properties: bool,
+    /// Canvas-space cursor position where Quick Properties was last opened.
+    quick_properties_anchor: Point,
     /// Selection cycling: clicking where objects overlap opens a list box
     /// to pick which one; the pick is added to the current selection.
     selection_cycling: bool,
@@ -2869,6 +2871,7 @@ impl OpenCADStudio {
             otrack_active: None,
             clean_screen: false,
             quick_properties: false,
+            quick_properties_anchor: Point::new(12.0, 12.0),
             selection_cycling: false,
             pick_add: true,
             pick_drag_rect: false,