Intermediate summary. Based on the results of the voting and discussion, the following was added to the Rules:

5.2. Hit-and-run is prohibited: the attacking hero is not allowed to retreat in the first round of battle if they cast any magic. This prohibition does not apply to the hero who is defending.

I removed the casting by units because, due to time constraints, I rushed it, and there wasn't enough discussion. Judging by the posts, players are mostly in favor of allowing it. The second formulation is the standard and common understanding of hit-and-run; in general, that's how we mostly played it, despite the unclear phrase:

...if he used combat magic or any other that, in one way or another, inflicted any damage to the enemy...

The arguments for the first one are simplicity and uniformity. We can come up with quite a few options, starting with a complete ban on retreating after casting any magic in any round (something similar existed, for example, in Times of Year) and ending with allowing it (which is also fine if you think about it; it just changes the game's tactics a little). But there should only be one option in the rules. I am removing the Important status from the topic, but I am not closing it. The discussion can continue. I would like to analyze real cases from current practice, i.e., to understand how the differences in the rule would affect the outcome of the game. And how often this happens. So, write...