Keep atuin on mise; nixpkgs is behind and its database will not downgrade

Keep atuin on mise; nixpkgs is behind and its database will not downgrade Taking atuin from Nix broke it on every prompt: Error: migration 20260818000000 was previously applied but is missing in the resolved migrations mise had 18.21.0 from upstream's own releases; nixpkgs has 18.19.0 on both unstable and master. 18.21 had already applied migration 20260818000000 to the local history database, and 18.19 refuses to open a database carrying a migration it does not know about. The database is 33 MB of real shell history, so downgrading was not an option and neither was resetting it. nixpkgs has no 18.21.0 to move to, so atuin goes back to mise as the single global exception, with the reason recorded in the config. It can move to Nix once nixpkgs catches up. This is the same shape as the per-project pins: mise tracks versions, nixpkgs tracks revisions, and for a tool whose upstream ships ahead of nixpkgs and whose on-disk state only moves forward, version tracking is what the job needs.