FINWDBLQNMWD moved back to zstd-seekable 0.1 but flake.nix still references 0.2 which makes the build fail

These changes work for me. The shell.nix change isn’t involved - it just ended up as a dependency

See also #552 where I have also fixed and proposed some changes to the nix build.

I’ve got further fixes to the Nix build as Rust edition 2021 is now required but the latest Pijul isn’t recording them correctly. Probably need to wait till this is fixed: https://pijul.zulipchat.com/#narrow/stream/270693-general/topic/file.20moving/near/262835900

Those changes probably aren’t useful without additional fixes to the Cargo.lock (yasna doesn’t have a conflict but is corrupted - missing the [[package]]) and Cargo.nix (via crate2nix generate) but I simply can’t record them currently as it’s claiming Error: Empty change even though the diff is not empty.

Turns out it’s the new change text writer/reader which is broken. Recording with --all works.

While I recognise flakes are extremely useful, I don’t use them myself (many reasons), so thanks for testing and fixing, I’ve just merged.