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

CLAUDE.md

@@ -148,7 +148,8 @@ Swarm-level:
 - **`swarm-matrix-ctl/`** — the one binary run inside
   `containers.hive-matrix`; new in-container jobs are verbs here, not
   crates.
-- **`swarm-builder/`** — builds agent config PR heads for commit status.
+- **`swarm-builder/`** — builds agent config PR heads for commit status,
+  and evaluates the agent archetypes the create form lists.
   Design: [`docs/swarm/builder.md`](docs/swarm/builder.md).
 - **`swarm-ci-metrics/`** — polls the forge's Actions runs and pushes each
   finished run's duration and queue wait to the metrics store. Design:
@@ -176,7 +177,8 @@ Swarm-level:
 - **`nix/`** — `host-modules/` (the host stack), `agent-modules/`
   (per-agent harness features), `container-modules/` (guest side of
   service containers), `templates/agent.nix` (the container entry
-  point), `packages/`, `docs/` (options doc), `module-eval/` (NixOS
+  point), `archetypes/` (the built-in agent archetypes), `packages/`,
+  `docs/` (options doc), `module-eval/` (NixOS
   module-eval tests), `builder/` (`check-flake`), `script-tests/`, plus
   `sources.nix` / `rust.nix` / `checks.nix` / `devshell.nix` /
   `treefmt.nix` behind the thin `flake.nix`.