Making post-quantum the default in a file format, not a toggle

Most "post-quantum" features I run into are a switch you have to find and flip. A

checkbox in settings, an opt-in beta, a separate "secure mode." I wanted the

opposite: the default at-rest cipher for every new file is post-quantum, and you

have to go out of your way to get anything weaker. This is a write-up of what

that actually took, the parts that were clean, and the parts that bit me. The