Builders pushed every path of a closure, including everything they had
substituted from cache.nixos.org: 9.9 of 10.3 GiB for ignavia. niks3 now
comes from a fork (lassulus/niks3) with `push --ignore-upstream-key`,
and neoprism's daemon and the CI farm pass cache.nixos.org-1 to it.

cache.lassul.us no longer holds complete closures on its own: clients
need cache.nixos.org next to it, which every machine has.

eternal-terminal 7.0.0 fails to build in the current nixpkgs (cmake_pch.hxx.gch), which failed green's toplevel in the CI farm.

Worker 2 of the first run had looked up paths before other builders pushed them, and its nix-daemon kept answering from the negative cache (1 h by default): 1118 'input not substitutable' retries until the machines failed.