This brazen attack directly from Iran into Israel is a massive escalation and, by any plausible definition, a declaration of war.

Nah. It's just an opportunity for Iran to probe Israeli defenses. Some useful intel was gathered to the extent any aspect of the defense was not designed as performative disinformation.

The players know what war looks like, and this ain't it. If Iran wanted to make war, a very different scenario would have played out, including an invasion by Hesbollah and a sea-based assault. Instead, there was a tit and there was a tat. (How was killing those generals not "a massive escalation and, by any plausible definition, a declaration of war"?)

No Israeli response is necessary. Israel's best move is to pretend that it will serve up some revenge later and wait for some real provocation actually to do something.