Child reconciliation does not close iterators when a yielded child throws

React version

Current main (2dc7da790d63).

Steps to reproduce

1. Render a synchronous or enabled asynchronous iterable as children.
2. Have its iterator implement return() (or generator cleanup in finally).
3. Yield an invalid child that makes reconciliation throw.
4. Inspect whether the underlying iterator is closed.

Current behavior

The reconciler manually consumes child iterators but does not call return() when child creation/update throws. Generator cleanup/resource release remains open. The async-iterable adapter also exposes only next(), so even shared close handling could not reach the underlying async iterator.

Expected behavior

Close each iterator exactly once on abrupt reconciliation, forward close through the async adapter, and preserve the original reconciliation error.

Start by reproducing the failure with synchronous and enabled asynchronous iterables, then locate the child reconciler's manual iterator consumption and the async-iterable adapter. Verify abrupt child errors, iterator return() or generator cleanup, and original-error preservation. Done means each iterator closes exactly once, async closure reaches the underlying iterator, and reconciliation still reports the original error.