It might be possible to trick them into combat. If you have your longest range sensor ships sensors turned off they might advance within missile range before encountering much shorter range sensors on other ships. Then you can turn on the long range sensors and get solid missile locks for long enough so the missiles can reach them.
I did this, and they stumbled upon my fleet; 10 seconds later they were the newest wrecks in the system. They still surprised me, though: their active sensor out-ranged my own, and I thought mine was far oversized compared to a standard sensor. I have never encountered precursor scouts in my previous games, and had assumed they were all missile cruisers. Although, in all my previous games I've never played enough to encounter anything
but precursors. . .