Who Owns Working Agreements
The Team's Responsibility
Working agreements belong to the team, not the facilitator. Imposed agreements fail.
Who Facilitates
In Scrum, the Scrum Master. In others, a team lead or external facilitator.
The facilitator can be the most senior person in the room; but be aware, when the director facilitates, people tend to create agreements they think leadership wants, not what they need. If you can find someone neutral - especially in teams that have a history of conflict - it is of great benefit.
Who Enforces Initially
In the first 30 days, someone needs to be the "bad cop." The team must designate someone to call out violations until it becomes a cultural norm.
This isn't about creating a monitor or policeman. It's about getting the team past the initial awkwardness of enforcement. Once calling out violations becomes normal, the designated role dissolves naturally.