swarm-ui: floating turn-state/model/ctx/cost badges on the agent term preview

Header-bar parity for the swarm-level agent terminal, per mara's ruling
"dont make it a header though - make it floating elements on top of the
terminal". Adds useSwarmAgentStateStream (SSE consumer for
swarm-controller's GET /api/agents/{name}/state/stream) and renders a
small read-only Badge cluster absolutely positioned in
AgentTermPreview's terminal box corner, reusing the same anchor pattern
@hive/shared/terminal.css's .tail-pill already uses.

Shows turn_state always, agent_state only when it isn't the boring "up"
case, model (with resolved-model tooltip), and ctx/cost usage. No badge
renders until the first header event lands - the swarm queue's
agent-state subject is transition-only with no seed/replay, and no
swarm-level endpoint today can seed turn_state/model/ctx/cost
synchronously.

Vocabulary (state tones, token-total/format helpers) ported from
@hive/agent's Root.tsx/lib/format.ts rather than imported, matching the
existing "small helper, not worth a cross-package hop" call
useSwarmTermStream's own appendRow already made.

Verified by rendering the real component tree against a stubbed
EventSource and screenshotting the result - the badge cluster initially
overlapped the terminal's first row of text, fixed by giving this
preview's own .live.terminal extra top padding.

frontend/packages/swarm-ui/src/pages/agents/AgentTermPreview.tsx

@@ -1,11 +1,23 @@
 // <AgentTermPreview> — the MVP mara's own ruling asked for: not a separate
 // page, a small read-only preview embedded below `AgentsPage`'s detail
-// panel fields. No header, no input — those (plus sending input back
-// to the agent) are explicitly follow-up scope, not this issue's.
-// Consumes swarm-controller's `GET /api/agents/{name}/term/stream` via
-// `useSwarmTermStream`, rendering through the same `@hive/shared`
-// `Row` component the per-hive local terminal uses — "share components
-// between hive and swarm level term as much as possible" (mara).
+// panel fields. No input — sending input back to the agent is explicitly
+// follow-up scope, not this issue's. Consumes swarm-controller's
+// `GET /api/agents/{name}/term/stream` via `useSwarmTermStream`,
+// rendering through the same `@hive/shared` `Row` component the per-hive
+// local terminal uses — "share components between hive and swarm level
+// term as much as possible" (mara).
+//
+// **Floating header badges** — turn state / model / ctx / cost parity
+// with the per-agent page's own `StatusChips` — mara: "dont make it a
+// header though - make it floating elements on top of the terminal", so
+// this is a small `Badge` cluster pinned to the terminal box's own
+// corner (`.terminal-wrap`'s `position: relative`, same anchor
+// `@hive/shared/terminal.css`'s `.tail-pill` already uses), not a
+// separate layout row. Read-only, no click targets: pause/resume already
+// has its own control surface (`WantedMenu` on `AgentsPage`), so nothing
+// here needs to be interactive. Sourced from `useSwarmAgentStateStream`,
+// not from `AgentRow` — the roster fetch `AgentsPage` already did has no
+// notion of turn_state/model/ctx/cost, only `wanted`/`snapshot.running`.
 import { useLayoutEffect, useRef, useState } from "preact/hooks";
 import { Badge, type BadgeTone } from "@hive/shared/badge.js";
 import { Row } from "@hive/shared/term-row.js";
@@ -13,6 +25,10 @@ import {
   useSwarmTermStream,
   type ConnectionState,
 } from "./useSwarmTermStream.js";
+import {
+  useSwarmAgentStateStream,
+  type TokenUsage,
+} from "./useSwarmAgentStateStream.js";
 import "./AgentTermPreview.css";
 
 const NEAR_BOTTOM_PX = 48;
@@ -31,13 +47,53 @@ const CONNECTION_TONE: Record<ConnectionState, BadgeTone> = {
   closed: "negative",
 };
 
+// Ported, not imported, same call `useSwarmTermStream`'s own `appendRow`
+// already made for this file's sibling hook: `@hive/agent`'s equivalents
+// (`STATE_LABELS`/`tokenTotal`/`fmtTokens` in `Root.tsx`/`lib/format.ts`)
+// live in a different package this one doesn't otherwise depend on, and
+// a cross-package hop isn't worth it for three small, stable helpers.
+// Vocabulary (glyphless — the per-agent page's own glyphs are part of
+// its bigger consolidated status badge, not this smaller read-only one)
+// kept in exact parity with `Root.tsx`'s `STATE_LABELS` so "idle" here
+// means the same thing it means there.
+const TURN_STATE_TONE: Record<string, BadgeTone> = {
+  idle: "neutral",
+  thinking: "accent",
+  compacting: "warning",
+};
+
+function tokenTotal(u: TokenUsage | null): number | null {
+  if (!u) return null;
+  // Matches `Root.tsx`'s own `tokenTotal`: input + both cache buckets,
+  // `output_tokens` deliberately excluded (shown in a title breakdown
+  // there, not carried at all here — this badge has no breakdown to put
+  // it in).
+  return (
+    (u.input_tokens ?? 0) +
+    (u.cache_read_input_tokens ?? 0) +
+    (u.cache_creation_input_tokens ?? 0)
+  );
+}
+
+function fmtTokens(n: number): string {
+  if (n >= 1_000_000) return (n / 1_000_000).toFixed(1) + "M";
+  if (n >= 1_000) return Math.round(n / 1000) + "k";
+  return String(n);
+}
+
 export function AgentTermPreview({ agentName }: { agentName: string }) {
   const { rows, connection } = useSwarmTermStream(
     `/api/agents/${encodeURIComponent(agentName)}/term/stream`,
   );
+  const { header } = useSwarmAgentStateStream(
+    `/api/agents/${encodeURIComponent(agentName)}/state/stream`,
+  );
   const logRef = useRef<HTMLDivElement>(null);
   const [stickToBottom, setStickToBottom] = useState(true);
 
+  const ctx = header ? tokenTotal(header.ctx_usage) : null;
+  const cost = header ? tokenTotal(header.cost_usage) : null;
+
   function handleScroll() {
     const el = logRef.current;
     if (!el) return;
@@ -61,6 +117,47 @@ export function AgentTermPreview({ agentName }: { agentName: string }) {
         value={CONNECTION_LABEL[connection]}
       />
       <div class="terminal-wrap ui-agent-term-preview-wrap">
+        {header && (
+          <div class="ui-agent-term-preview-header-badges">
+            <Badge
+              tone={TURN_STATE_TONE[header.turn_state] ?? "neutral"}
+              value={header.turn_state}
+            />
+            {/* Only the non-boring case gets a badge — a healthy running
+                agent (`agent_state: "up"`) doesn't need one for the
+                obvious default. In practice this only ever fires for
+                "paused": `hive-agent` can only honestly publish "up" or
+                "paused" on this subject (see `AgentStateMsg::agent_state`'s
+                own doc), never "offline"/"destroyed" — a stopped or
+                destroyed agent publishes nothing at all. */}
+            {header.agent_state !== "up" && (
+              <Badge tone="warning" value={header.agent_state} />
+            )}
+            <Badge
+              label="model"
+              value={header.model}
+              title={
+                header.resolved_model
+                  ? `resolved to ${header.resolved_model}`
+                  : undefined
+              }
+            />
+            {ctx !== null && (
+              <Badge
+                label="ctx"
+                value={fmtTokens(ctx)}
+                title="tokens used in the current context window"
+              />
+            )}
+            {cost !== null && (
+              <Badge
+                label="cost"
+                value={fmtTokens(cost)}
+                title="cumulative tokens billed across the last turn"
+              />
+            )}
+          </div>
+        )}
         <div class="live terminal" ref={logRef} onScroll={handleScroll}>
           {rows.length === 0 ? (
             <div class="row note">