v4.2.2: fix: Resolve change set references regardless of definition order

Previously, `$ref` entries in change sets would fail to resolve if their corresponding `$id` definition appeared later in the document. This led to `UnexpectedValueException` and unreadable change log entries.

This change pre-registers all `$id`s found in the document with empty `ChangeSet` instances before decoding begins. This ensures that any `$ref` can find its target instance, allowing for correct resolution even when `$ref` precedes `$id` in the document structure.