mara: "no, do split packages for the separate daemons" — instead of
grouping all daemon/harness/MCP bins into one hyperhive-daemon
derivation, each bin (hive-c0re, hive-priv, hive-agent,
hive-agent-mcp, hive-agent-wake, hive-bash-daemon, hive-bash-mcp,
hive-matrix-daemon, hive-matrix-mcp, hive-metric) is now its own
named package + overlay output, matching the existing hivectl /
hive-forge split. harness-base.nix's ExecStart/command lines now
point at the specific pkgs.hive-* each ExecStart needs, and
environment.systemPackages only carries the two bins actually
PATH-looked-up in-container (hive-agent-wake, hive-metric) instead
of the whole bundle.