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

docs/swarm/services.md

@@ -330,3 +330,23 @@ secret store by name, under its own `review-classifier` leaf. On a host
 without the store, that leaf is the one file to copy, as for the CI runner.
 The swarm UI's try-out drives it through swarm-controller; what a run is
 and what it costs are in [`review-classifier.md`](review-classifier.md).
+
+### Claude login minter
+
+The claude login minter, in a `swarm-claude-login` container on the host that
+sets `deploy.claude-login.enable`. `allSwarmServices` defaults it on wherever
+the host has the minter's store identity, on the review classifier's terms.
+Run one: a login in progress lives in the service's memory between its start
+and its code.
+
+An operator logs an agent in from the **log in** button on its card in the
+swarm UI. swarm-controller relays the start and the pasted code over the queue,
+the minter runs `claude auth login` and writes the credentials to the agent's
+`swarm/agents/<agent>/claude-credentials`, and the agent's harness installs a
+version newer than the one it installed last.
+
+It needs neither the forge nor a hive on its host. It reaches the queue and the
+secret store by name, under its own `claude-login` leaf, and reaches claude's
+login endpoints over the network. On a host without the store, that leaf is
+the one file to copy, as for the CI runner. The flow and the version rule are
+in [`claude-login.md`](claude-login.md).