Diverged quite a lot:

https://manifold.markets/SemioticRivalry/will-israel-hit-iranian-nuclear-sit

How clear must Israel's culpability be? Often attacks are widely believed to be perpetrated by Israel for clear circumstantial reasons, yet no solid confirmation can be found (e.g. the pager attack this year, stuxnet)

Do cyber attacks or sabotage count?

All attacks count but there needs to be some damage.

What if it is indirect, for example an air defense system that protects nuclear facilities like in the last attack?

Attack needs to be directed at nuclear facilities.

These are ambiguous answers. Does "damage" mean physical damage? A cyber attack might just shut systems off for a few hours. Would that count? Is the attack on the air defense system guarding a nuclear facility "directed" at the nuclear facility or at the defense installation? You didn't say.