Function useCardPivot

Helper for card content that opens objects (e.g. a related-object link): attach ref to the card's root element, then pass the returned id as the Open pivotId with disposition: 'add', so navigation always adds a plank beside the card's own plank rather than replacing the deck. The card's outermost attendable ancestor is its plank, so the pivot is resolved structurally once mounted (see Attention.getRootAttendableId) and is undefined until then, which no menu action can observe.