I have a 96 and my windshield is glue in but I did look for rust perforation. My first thought was to look there.

I will look further for the drains you mentioned. My plenum, under the cowl panel, drains behind the fender via a "trough" below the area where the wiper transmissions mount.

I have thought about buying one of those small inspection cameras and poking around with it or pulling the entire dash and see if there is anything to see...

The truly weird thing about this leak is it seems to be a hole straight to the open sky! It lets water in when there is a heavy dew even. No driving at all required! Yet I still cannot get it to leak with any other source of water. I'm pulling my hair out! I tried a dye in hopes of using a black light to find the source but cannot get it to leak other than "natural" sources! GRRRRRR....