Eight classifications in .hyperhive/review-classifier.yml: no AI
advertising in commit messages, no committed secrets, no clippy
allow attributes, no debug leftovers, no dead code, tests with
behaviour changes, docs with operator-facing changes, one purpose per PR.
A swarm-controller test parses the real file so it can't rot, and the
rust source fileset in nix/rust.nix includes it so the test finds it
in the build sandbox.
