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• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• All existing tests are passing: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/DevelopmentWorkflow.md#running-unit-tests-application.
• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

What is the current behavior?

When ProxyViewContainer.hidden = true is set, the container's isCollapsed property is set correctly for layout calculations, but the child views remain visible because ProxyViewContainer has no native view. Since children are directly added to the parent's native view tree, they need to have their hidden property set individually to be visually hidden.

This is described in issue #10912.

What is the new behavior?

When ProxyViewContainer.hidden = true is set, the hidden state is now properly propagated to all child views, making them visually hidden. The fix:

1. Added _applyHiddenToChildren method: Iterates through all child views and applies the hidden state to each one.

2. Overrode hiddenProperty for ProxyViewContainer: Registered a custom property handler that:

   • Sets isCollapsed for layout calculations (preserving existing behavior)
   • Calls _applyHiddenToChildren to propagate the hidden state to all children

3. Updated _addViewToNativeVisualTree: When a new child is added, if the container is already hidden, the child's hidden property is immediately set to true.

This ensures that when ProxyViewContainer.hidden = true is set, all existing and future children are properly hidden, matching the expected behavior.

Fixes #10912.