IME focus lost behavior feels weird / wrong

I think the implemented behavior in this case feels strange

When I type some unfinished Chinese or Japanese and then click away from the text box while the IME popup is active, it clears the text and the IME popup is still there. I assume from the documentation that this is intentional (although personally I would think the IME popup should also be cleared…)

But when I click back into the field and start typing again, the text that I thought would be cleared appears back again. Is this how IME is supposed to work?

Beyond that, personally, I wonder it would feel more natural if `on_focus_lost` just commits the composition as is. It feels off that navigating away from a field would do what appears to be backspacing. When I type something using IME in a search bar on the web and click away, what I typed stays there

_Originally posted by @kfc35 in https://github.com/bevyengine/bevy/pull/23841#discussion_r3114872057_