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

swarm-nats-auth/src/main.rs

@@ -167,6 +167,11 @@ struct Args {
     #[arg(long = "builder-client")]
     builder_clients: Vec<String>,
 
+    /// Client ids that answer the claude login minter's login requests.
+    /// Repeatable, empty by default, which denies such a client.
+    #[arg(long = "claude-login-client")]
+    claude_login_clients: Vec<String>,
+
     /// Role on the secret store's `cert` auth mount this responder logs in
     /// as to read the callout keys, its own OIDC client secret and agent
     /// credentials. The store is found
@@ -232,7 +237,8 @@ async fn serve(args: &Args) -> anyhow::Result<()> {
     )?
     .with_agent_token_subjects(args.agent_token_publish_subjects.clone())?
     .with_review_classifiers(args.review_classifier_clients.clone())
-    .with_builders(args.builder_clients.clone());
+    .with_builders(args.builder_clients.clone())
+    .with_claude_logins(args.claude_login_clients.clone());
     let http = reqwest::Client::new();
     let settings = swarm_secret_client::client::Settings::from_env()
         .context("reading the secret store's address and this responder's identity")?;