agent page: inbox view of last 30 messages addressed to this agent

new wire request AgentRequest::Recent { limit } / ManagerRequest::Recent
(plus matching responses with Vec<InboxRow>). InboxRow moved to
hive-sh4re so it lives on both surfaces without an internal-to-wire
conversion. host-side dispatch in agent_server / manager_server
calls broker.recent_for(name, limit).

per-agent web_ui /api/state grew an inbox: Vec<InboxRow> populated
via the same per-agent socket (best-effort; transport failure
returns empty). frontend renders as a collapsible <details> section
between the state row and the terminal — fmt timestamp / from /
body in a tight grid, capped at 16em scrollable. only visible when
there are rows.

hive-ag3nt/assets/app.js

@@ -337,6 +337,30 @@
     }
     renderStateBadge();
   }
+  function renderInbox(rows) {
+    const root = $('inbox-section');
+    const list = $('inbox-list');
+    const summary = $('inbox-summary');
+    if (!root || !list || !summary) return;
+    if (!rows.length) {
+      root.hidden = true;
+      return;
+    }
+    root.hidden = false;
+    summary.textContent = 'inbox · ' + rows.length;
+    list.innerHTML = '';
+    const fmt = (n) => new Date(n * 1000).toISOString().replace('T', ' ').slice(5, 19);
+    for (const m of rows) {
+      const li = el('li');
+      li.append(
+        el('span', { class: 'inbox-ts' }, fmt(m.at)), ' ',
+        el('span', { class: 'inbox-from' }, m.from), ' ',
+        el('span', { class: 'inbox-sep' }, '→'), ' ',
+        el('span', { class: 'inbox-body' }, m.body),
+      );
+      list.append(li);
+    }
+  }
   function renderLastTurn(ms) {
     const el_ = $('last-turn');
     if (!el_) return;
@@ -386,6 +410,7 @@
       const s = await resp.json();
       if (!headerSet) { setHeader(s.label, s.dashboard_port); headerSet = true; }
       renderTermInput(s.label, s.status === 'online');
+      renderInbox(s.inbox || []);
       // Drive the state badge from the harness status. Live SSE events
       // override to 'thinking' / 'idle' as turns start/end; this only
       // kicks in for the not-online (offline) case and the initial seed.