Saving an automatic child warns Undefined array key parents and does not save

Problem/Motivation

Saving a node that is an automatic child prints two PHP warnings and the save does not complete, so Autopilot never rewrites the menu title:

• Undefined array key "#parents" in FormState::getError()
• foreach() argument must be of type array|object, null given (same function)

The owned-child notice is injected in #after_build after the form is processed, so it has no #parents. FormErrorHandler then calls getError() on it whenever any validation error exists. Hiding menu_ui also leaves enabled=0 and drops weight/parent, so a pending revision hits MenuSettingsConstraint. That error sits on the inaccessible menu widget, so the editor only sees the PHP warnings. Because the form does not submit, hook_entity_update never runs and escaped titles from the 1.2.2 token fix are not rewritten.

Steps to reproduce

1. Enable automatic children on a parent.
2. Edit a published automatic child (content moderation on).
3. Save (including as a draft / pending revision).
4. The warnings appear and the node is not saved. The menu title is unchanged.

Proposed resolution

Stamp #parents and #array_parents on the notice. Restore the live link title, weight, and parent onto form state so a draft save does not look like a menu-settings change. Keep menu_ui from writing the managed child.

Remaining tasks

• Kernel tests
• Patch
• 1.2.3 release

User interface changes

None. The same notice still appears in Advanced.

API changes

None.

Data model changes

None.