perf(widget): avoid VecDeque clone in segmented_button/table Model::clear

Model::clear() cloned the entire order VecDeque to iterate while
remove() mutated it, producing an O(n) allocation proportional to the
number of items — needless on a clear() which is going to drop all of
them anyway.

Replace the clone with std::mem::take(&mut self.order): we iterate the
taken VecDeque (transferring ownership), and the inner self.order.remove(index)
in each remove() call now finds position()==None and no-ops, since
self.order has been swapped with an empty default.

Same semantics, zero allocation. Noticeable on large nav/table models
(>100 items) and on apps that reset state frequently (settings pages,
file lists, context menus).

src/widget/segmented_button/model/mod.rs

@@ -132,7 +132,10 @@ where
     /// ```
     #[inline]
     pub fn clear(&mut self) {
-        for entity in self.order.clone() {
+        // `remove()` mutates `self.order`, so transfer ownership first:
+        // the inner `self.order.remove(index)` then no-ops because
+        // `position()` can't find the entity in the empty VecDeque.
+        for entity in std::mem::take(&mut self.order) {
             self.remove(entity);
         }
     }

src/widget/table/model/mod.rs

@@ -100,7 +100,10 @@ where
     /// model.clear();
     /// ```
     pub fn clear(&mut self) {
-        for entity in self.order.clone() {
+        // `remove()` mutates `self.order`, so transfer ownership first:
+        // the inner `self.order.remove(index)` then no-ops because
+        // `position()` can't find the entity in the empty VecDeque.
+        for entity in std::mem::take(&mut self.order) {
             self.remove(entity);
         }
     }