I can't find any info on attaching cortosis to a melee weapon. Was that missed? Does anyone have the stats for this?

The debs have clarified that there are things in the book intended for "forward compatibility."

In the core rules, there's nothing about how to add cortosis to a weapon, but you at least have rules for how it works in case someone finds something, for instance.

My ultimate Jedi killer vibro-axe will have to wait.

If your GM allows it, you could apply the cortosis weave armor attachment to your vibro-ax, making it unsunderable. Or are you looking for the cortosis ability to short out lightsabers? If the latter then it is only mentioned under the cortosis quality. Probably to have mechanics at a later date in Force & Destiny. Perhaps something along the lines of running out of ammo on a despair (or even, as with the heavy blaster, with three threats or a despair), your lightsaber shorts out for a certain amount of rounds.

Yeah, as of the setting, cortosis isn't that popular, since the lightsabers it pisses off aren't frequent. I think there were some specialist Clone Troopers who had some cortosis stuff, and one Jedi Master who tried to kill Vader, and in turn got herself and the other Masters she brought with her killed when Vader showed that someone great with a lightsaber will also be pretty good with a sword, especially against Jedi with no back up weapons, who are unwilling to use the Force to hurt someone. She shorted out his lightsaber, he cocked his head, Force-pulled the sword to him, and butchered everyone present. He kept the sword, so it's probably in the same phrik locker Obi-Wan's lightsaber was in.

Beyond those, cortosis is probably a thing from long ago (Kotor), and might show up there, or in Legacy, where Imperial Knights where gauntlets made of the stuff. In this time, it would MOSTLY be a very expensive decoration, while you'll never see a lightsaber. All IMO, of course.

Someone on my ship got cortosis put in his armor so he can't be pierced or breached. I also want cortosis on a vibro-axe so my weapon can't be sundered by another axe.

Cortosis infused/weaved weapons and armor aren't that special. Its not like metal, laminate based armors. Its sole use is it shorts out lightsaber based weapons. Infusing it is one thing, using a weapon made of the stuff would be pointless, its like shale, it easily crumbles.

But in this game it makes armor immune to breach and pierce and makes weapons immune to sunder

Cortosis infused/weaved weapons and armor aren't that special. Its not like metal, laminate based armors. Its sole use is it shorts out lightsaber based weapons. Infusing it is one thing, using a weapon made of the stuff would be pointless, its like shale, it easily crumbles.

If you read the Cortosis quality in the book, it talks about using cortosis alloys, specifically, which make weapons immune to Sunder and Armor immune to Breach and Pierce.