hive-meta-flake

The meta flake's flake.nix text: one nixosConfigurations.<agent> per agent, each built from hyperhive's agent-base plus the agent's config input or archetype.

Pure string rendering, with no IO and no environment reads. The caller passes the hyperhive pin, the agents with their pins, and the values every agent container gets. swarm-controller calls render_flake; hive-c0re reads the pins of the flake it renders (pinned_rev, builds_agent_at).