swarm UI: an agent that needs a Claude login shows it on its card

The agent's turn-state header ($SWARM.agent-state.<agent>) gains
`needs_login`, set by hive-agent from its own LoginState, so the flag
reaches the swarm without hive-c0re (mara on #5268: "id prefer the agent
container sending the info it needs login without hive").

- swarm-queue-client: `agent_login::Login`, the shared wire type, beside
  `agent_inference::Effective`. `needs_login: Option<bool>` with
  `#[serde(default)]`: a header from an older agent decodes as `None`
  (unknown), never as "needs login" or "logged in".
- hive-agent: the header publisher reads the shared LoginState cell.
  Every writer of that cell emits a status on the bus afterwards, so a
  login change goes out on the next rebuild, not the 60 s refresh.
- swarm-controller: `agent_login::Reported` follows every agent's header
  and keeps the latest flag; `GET /api/agents/status` merges it into each
  row as `needs_login` (null when unknown).
- swarm-ui: AgentCard shows a warning-tone "login needed" badge when the
  row's `needs_login` is true.

Refs #5268

frontend/packages/swarm-ui/src/agent/roster/AgentCard.tsx

@@ -17,7 +17,7 @@ import type { ProblemDetails } from "@hive/shared/api-error.js";
 import { Card } from "../../ui/card/Card.js";
 import { RelativeTime } from "../../ui/relative-time/RelativeTime.js";
 import { AgentIcon } from "../AgentIcon.js";
-import { FRESHNESS, type AgentRow } from "../AgentTypes.js";
+import { FRESHNESS, showsLoginNeeded, type AgentRow } from "../AgentTypes.js";
 import { WantedMenu } from "./WantedMenu.js";
 import "./AgentCard.css";
 
@@ -71,6 +71,13 @@ export function AgentCard({
                 </>
               }
             />
+            {showsLoginNeeded(row) ? (
+              <Badge
+                tone="warning"
+                value="login needed"
+                title="the agent's claude has no session; its turns wait until it is logged in"
+              />
+            ) : null}
             <span
               class="ui-agent-card-wanted"
               onClick={(e) => e.stopPropagation()}