Details toggle event does not report reason for toggle

[legowerewolf]

What is the issue with the HTML Standard?

By this I mean specifically that there is no way to tell whether a details element was toggled by a user clicking on its summary element, a user clicking on the summary element of another details element with the same name, or some other reason.

Having this reason on the "toggle" (and elsewhere-mentioned "beforetoggle" #9743) events would simplify logic around, for example, tab-like interfaces where one of a set of details elements should always be open.