function GetEditJournalInfo: TPdfEditJournalInfo;
Returns the journal snapshot covering TransactionActive, EntryCount, Position, StoredBytes, CanUndo and CanRedo availability, the adjacent UndoLabelText and RedoLabelText, and the SHA-256 RootFingerprint and CurrentFingerprint
After oldest-entry eviction, RootFingerprint advances to the earliest state that is still represented by the retained journal