Eventually the plan will be to move away from OSH entirely for f_scripts.

Use oil for shebang line and shopt -s oil:all per: https://www.oilshell.org/release/latest/doc/deprecations.html#right-now-shopt-s-oilbasic

This isn't really feasible / this is blocked until oil supports some sort of API / language stability guarantees which it seems is slated for oil 1.0. See: https://github.com/oilshell/oil/issues/973