swarm UI: log an agent into claude from its card; the credentials go to bao and the agent picks them up

A new swarm service, `swarm-claude-login`, in its own container on the host
that sets `deploy.claude-login.enable` (defaulted on by `allSwarmServices`
where the host has the minter's store leaf, like the review classifier).

- swarm-ui: an agent card showing "login needed" gets a "log in" button.
  Its dialog starts the login, shows the URL claude printed, and takes the
  pasted code.
- swarm-controller: `POST/DELETE /api/agents/{name}/claude-login` and
  `POST /api/agents/{name}/claude-login/code`, behind the swarm UI's
  authelia-gated `/api/`, relay the steps to the minter as requests on
  `$SWARM.claude-login.request`.
- swarm-claude-login: runs `claude auth login` over piped stdio with HOME
  and CLAUDE_CONFIG_DIR in a per-login scratch dir, scrapes the first
  https URL, writes the code to stdin, and stores the `.credentials.json`
  at `swarm/agents/<agent>/claude-credentials` with a KV v2 write, a new
  version over any earlier one. The scratch dir goes on every exit path; a
  login waits 15 minutes for its code.
- hive-agent: while parked in `wait_for_login`, reads that leaf every 30 s
  under the agent's own cert and installs it only when its KV version is
  newer than the one recorded in `<harness>/claude-credentials-version`.
  An equal or older version is never put back, because claude rotates the
  refresh token and the stored copy is stale after the first refresh.
- swarm-secret-client: `claude_login` paths and `SecretStore::read_versioned`.
- Credentials: a `claude-login` store leaf minted by glue-bao-tls, a
  `swarm-claude-login` policy (create/update on
  `swarm/agents/+/claude-credentials`, read on its own queue client
  secret), an authelia machine client, and a `--claude-login-client`
  grant in the queue's auth-callout responder. The unit runs as a static
  system user.

The hive's own web-UI login is unchanged.

Refs #5268

nix/module-eval/core-toggle.nix

@@ -365,6 +365,27 @@ let
         && lib.hasInfix socket l."/webhook/forge/".proxyPass
         && !(lib.hasInfix "auth_request" l."/webhook/forge/".extraConfig);
     }
+    {
+      # nginx serves a path from its longest matching prefix location, so that
+      # one must be the gated `/api/`, and no exact location may take a route
+      # out from under it.
+      name = "the claude login routes reach the controller only through a location that asks authelia";
+      ok =
+        let
+          l = allLocal.services.nginx.virtualHosts."t.local".locations;
+          route = "/api/agents/a/claude-login/code";
+          covering = lib.filter (
+            name: !(lib.hasPrefix "~" name) && !(lib.hasPrefix "= " name) && lib.hasPrefix (prefix name) route
+          ) (lib.attrNames l);
+          prefix = lib.removePrefix "^~ ";
+          longest = lib.foldl' (
+            a: b: if lib.stringLength (prefix b) > lib.stringLength (prefix a) then b else a
+          ) "" covering;
+        in
+        longest == "/api/"
+        && lib.hasInfix "auth_request /__hive_authelia;" l.${longest}.extraConfig
+        && !(lib.any (name: lib.hasPrefix "= /api/agents" name) (lib.attrNames l));
+    }
     {
       name = "a hive with matrix off serves no matrix discovery endpoint";
       ok =