The fix-lockfiles script used 'nix build .#tui.npmDeps' to detect stale
hashes. This always succeeds when the OLD derivation is cached in Cachix
or cache.nixos.org — even when the source package-lock.json has changed.
Fix: use prefetch-npm-deps to compute the hash directly from the lockfile
and compare against what's in the nix file. Falls back to nix build only
if prefetch-npm-deps fails.
13a7cbcd64