Preserve ResponsiveRow child state across Row/Wrap layout switches (#6663)

* ResponsiveRow: preserve child state across Row/Wrap layout switches

Key each child's ControlWidget with a GlobalObjectKey tied to its Control
identity so Flutter re-parents existing elements when the layout flips
between Row and Wrap on a breakpoint change, instead of unmounting and
re-inflating the subtree. Stateful descendants (video players, WebViews,
scroll positions) now survive window resizes across breakpoints.

Fixes #6661

* add changelog entry

Author: FeodorFitsner

CHANGELOG.md

@@ -49,6 +49,7 @@
 * Fix `ProgressRing.year_2023` being ignored, so the control correctly switches between the latest and 2023 Material Design appearances ([#6614](https://github.com/flet-dev/flet/issues/6614)) by @ndonkoHenri.
 * `flet build ipa` / `ios` apps that ship ctypes packages with plain `.dylib` shared libraries (e.g. `llama-cpp-python`) now load them on the **iOS simulator** instead of failing at launch with a `dlopen` platform mismatch (`have 'iOS', need 'iOS-simulator'`); the iOS runtime also now bundles the `_multiprocessing` extension (importable, not spawnable). Bumps the pinned bundle to `serious_python` 4.2.1 / python-build `20260701` ([serious_python#223](https://github.com/flet-dev/serious-python/pull/223)) by @ndonkoHenri, @FeodorFitsner.
 * Improve performance of checking added/removed controls in Session.patch_control from O(N²) to O(N) ([#6651](https://github.com/flet-dev/flet/pull/6651)) by @davidlawson.
+* Fix stateful controls inside `ResponsiveRow` (video players, WebViews, scroll positions) losing their state whenever a window resize crossed a breakpoint and the layout switched between a single row and wrapping ([#6661](https://github.com/flet-dev/flet/issues/6661), [#6663](https://github.com/flet-dev/flet/pull/6663)) by @FeodorFitsner.
 
 ### Documentation
 

packages/flet/lib/src/controls/responsive_row.dart

@@ -79,10 +79,16 @@ class ResponsiveRowControl extends StatelessWidget with FletStoreMixin {
             childWidth = 0;
           }
 
+          // Key the child with a GlobalKey tied to its Control identity so
+          // that when this build switches between Row and Wrap (a different
+          // widget type at the same slot), Flutter re-parents the existing
+          // Element instead of re-inflating the subtree — otherwise stateful
+          // descendants (video players, WebViews, scroll positions) would
+          // lose their State on every breakpoint change.
           controls.add(ConstrainedBox(
             constraints:
                 BoxConstraints(minWidth: childWidth, maxWidth: childWidth),
-            child: ControlWidget(key: key, control: ctrl),
+            child: ControlWidget(key: GlobalObjectKey(ctrl), control: ctrl),
           ));
         }