archetypes: prefill the create form from flake-declared agent archetypes

A flake declares agent archetypes in its `hyperhiveArchetypes` output,
`<name> = { module; meta; }`. The hyperhive flake ships `reviewer`
(default permissions without `execution`).

swarm-builder answers `$SWARM.builder.archetypes` with the `meta` of
every archetype its own hyperhive source declares. swarm-controller asks
once the queue connects and every 10 minutes, checks each archetype as
`POST /api/agents` checks its settings, and stores the result in the
`agent-archetypes` KV bucket when it changed. `GET /api/archetypes`
serves it, and the create form's archetype select prefills permissions,
resource caps and inference from it.

The agent created is an ordinary agent with its own config repo; the
archetype's module is not applied yet.

Refs #5386

flake.nix

@@ -206,6 +206,10 @@
           agent-base = mkContainer self.nixosModules.agent-base;
         };
 
+      # Agent archetypes, `<name> = { module; meta; }`. Not per system: `meta`
+      # is plain data, and `module` takes its `pkgs` from the agent's system.
+      hyperhiveArchetypes = import ./nix/archetypes;
+
       devShells = forAllSystems ({ pkgs, rust, ... }: import ./nix/devshell.nix { inherit pkgs rust; });
 
       formatter = forAllSystems ({ treefmt-eval, ... }: treefmt-eval.config.build.wrapper);