I'll Support this.
Since getting new wolves is highly reliant on Encounters at the moment, it would be nice to have a warning before exploring, or an ability to buy new slots when successfully befriending a wolf while having no slots.
Since the Exploration mechanic is used for food, materials, activities, etc. It's not an easy thing to have to purposefully avoid just so you don't miss a Wild Wolf because you don't have the space and can't afford it at the moment.