If you have a good enough memory, you can memorize a wallet seed. There's no seizing that.

this is the way

To be pedantic, I don’t think they can hold you in contempt without also involving you in the process, giving you some legal say to fight it. The whole issue with civil asset forfeiture is that it divorces the property from its owner, legally speaking.

You should research this. A judge can order you to provide the passphrase to decrypt the storage that contains the bitcoin wallet if it is a foregone conclusion that there is one on there, and if you refuse then you can be held in contempt and jailed until you do provide it. There is no time limit to contempt of court imprisonment because you are free to stop being in contempt whenever you choose. You will have a very hard time getting an appeals court to issue a mandamus order to the judge that jailed you for contempt, and by "hard" I mean "impossible".

Yes but those aren’t civil asset forfeiture cases, which this discussion is about.