Great question.

While I have four salient feature for building a TDG, the definition of consensus is not one of them. Each TDG will figure this out for themselves.

There will be different experiments in TDG governance.

My recommendation is that an issue should have sufficient discussion and reflection, If full consensus is not reached, then a majority vote should suffice. The TDG will move in that direction and learn by taking action, not by arguing. Part of that learning will be about the level of consensus as you have outlined.