[theeket]

Summary:

Related to #59166. This change addresses the unmount comparison; it does not reset container state during recycling.

Unmounting a zero-sized recycled View can fail with Attempt to unmount a view which is mounted inside a different view, even when the exception reports the parent's own tag as the existing parent.

A previous owner can leave the native view with a clipping container, for example when using overflow: 'hidden' with an outline. Fabric can mount descendants before applying the recycled parent's new props. If those props no longer require the container and the view has zero bounds, layer invalidation returns without migrating the children back.

currentContainerView performs that migration lazily. The unmount assertion compares childComponentView.superview == self.currentContainerView, so evaluation can read the child's old superview before the getter moves it. By the time the exception message is formatted, the child can already belong to the expected parent.

Resolve the container in a separate statement before reading superview in the assertions. The reconciliation also runs when assertions are disabled. Existing ownership and index checks remain unchanged.

Changelog:

[IOS] [FIXED] - Reconcile recycled view containers before checking child ownership during Fabric unmount.

Test Plan:

Added native regression tests for:

• A clipping-container owner being recycled, receiving a new child before its props update, and then being unmounted at zero size after the container is no longer required. The test checks that unmount does not assert, detaches the child, and removes the stale container.
• A child that actually belongs to another parent still producing an ownership assertion.

The lifecycle sequence above is constructed directly with RCTViewComponentView; it is not an end-to-end JavaScript/Fabric reproduction. Its assertion behavior can depend on operand evaluation order before the fix.

The RCTViewComponentViewUnmountTests.mm passed.
Real application tested on react-native 0.88.1 with iOS 27.2 device, Xcode 27.1.

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