A bare `nix store ping` run as root with the daemon socket absent
resolves to a local store (root writes /nix/store directly) and pings
successfully, so the gate could false-pass at cold boot: nix-daemon.socket
carries ConditionPathIsReadWrite=/nix/var/nix/daemon-socket and is
condition-skipped until /nix/var goes read-write. systemd service units
don't source the profile that sets NIX_REMOTE=daemon, so auto-store
fallback to local is the real environment here.
Pin --store daemon so the readiness poll verifies the actual daemon
socket and the gate honours its wait-for-daemon contract instead of
passing against a local fallback while the daemon is still down.
2efd95d0f5