Resolves YES if one country attacks another country with a nuclear weapon for reasons that are clearly a part of the Russia-Ukraine conflict. Resolves NO if the conflict is resolved without any such detonations.
A "resolved" confict means that we reach a state of affairs where it doesn't seem likely that one country will use force against another any time in the near future. They don't have to actually be friendly with each other, but there do need to be no threatening troop movements or nonviolent attacks such as government-sponsored hacks or aggressive economic sanctions.
A nuclear test meant to intimidate an opposing country doesn't count.
Also see https://manifold.markets/ChristopherKing/russia-coupnuke-combination-market?r=Q2hyaXN0b3BoZXJLaW5n