swarm-ui: full-tab agent terminal (#4506)

Adds a full, non-capped agent terminal reachable from a new expand
trigger on the embedded AgentTermPreview (the detail-panel preview on
AgentsPage stays as-is, just gains the trigger). Opens
/agents/:name/terminal in a new dynamic tab in Shell's header, next to
the static nav row — tabs persist across a reload via useDynamicTabs,
a small localStorage-backed hook built on @hive/shared's existing
settings-storage primitive.

AgentTermPreview gains two new props to support both mounts from one
component: fullHeight (drops the 12em preview cap, fills its page)
and showHeaderBadges (default true — lets a future caller that
already shows turn_state/model/ctx/cost elsewhere suppress this
cluster; AgentsPage doesn't use it, see below).

Deviation from the originally posted plan (issue comment 80596): that
plan proposed AgentsPage's embedded preview pass showHeaderBadges as
false, reasoning the detail panel already duplicates that info.
Checked the actual code before implementing — it doesn't; AgentRow/
AgentTypes.ts carry none of turn_state/model/ctx/cost, and
AgentTermPreview's own floating badges are the only place swarm-ui
shows them. Left the badges visible there instead of shipping a
regression the plan's own stated justification didn't hold up to.

Also fixed a same-tab pub/sub race found by actually rendering a cold
load of /agents/:name/terminal (headless chromium, not just reasoning
about the code): useLocalSetting subscribes inside a useEffect, and
mount effects fire children-before-parents, so a descendant's
mount-time write (AgentTerminalPage registering its own tab) can beat
an ancestor's (Shell's) subscription into existence, leaving Shell's
tab row silently empty on a direct/reload load. Fixed by having
useDynamicTabs re-sync from storage on every location change, not
just on notify() — the fix lives in the new hook itself, not in the
shared settings-storage primitive theme/motion overrides also use.

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

@@ -0,0 +1,42 @@
+// <AgentTerminalPage> — the swarm terminal tab's full page, mounted at
+// `/agents/:name/terminal`. The MVP `AgentTermPreview` (below `AgentsPage`'s
+// detail panel) is explicitly capped and read-only; this is that same
+// component's `fullHeight` mount — no 12em cap, floating header badges
+// shown (there's no detail-panel `<dl>` here to duplicate them). Sending
+// input back to the agent is still explicit follow-up scope, same as the
+// preview's own file comment says — this page doesn't change that.
+//
+// Registers itself in the dynamic-tabs row on mount (not just when opened
+// via the preview's expand trigger) — a bookmark, a shared link, or a
+// plain page reload should all re-open the tab instead of landing on a
+// page with no way back into the tab row. `useDynamicTabs().open()` is
+// idempotent (dedupes by href), so this is safe to call every mount.
+import { useEffect } from "preact/hooks";
+import type { RouteComponentProps } from "wouter-preact";
+import { AgentTermPreview } from "./AgentTermPreview.js";
+import { useDynamicTabs } from "../../shell/useDynamicTabs.js";
+import "./AgentTerminalPage.css";
+
+export function AgentTerminalPage({
+  params,
+}: RouteComponentProps<{ name: string }>) {
+  const { open } = useDynamicTabs();
+  const name = decodeURIComponent(params.name);
+
+  // Runs once per mounted agent name — re-registering on every render
+  // would just be redundant work against an already-deduped list, but
+  // there's no reason to pay it more than once per identity.
+  useEffect(() => {
+    open({ href: `/agents/${encodeURIComponent(name)}/terminal`, label: name });
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- `open` is a
+    // fresh function identity every render (`useDynamicTabs` doesn't
+    // memoize it); including it would re-fire this effect every render
+    // instead of once per agent `name`.
+  }, [name]);
+
+  return (
+    <div class="ui-agent-terminal-page">
+      <AgentTermPreview agentName={name} fullHeight showHeaderBadges />
+    </div>
+  );
+}