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.

TODO.md

@@ -27,12 +27,6 @@ Pick anything from here when relevant. Cross-cutting design notes live in
 
 ## UI / UX
 
-- **Per-agent inbox view.** Show the last N messages addressed to
-  this agent on its page (the per-agent equivalent of the
-  dashboard's operator inbox). Needs a new wire request from agent
-  → host (host has the broker; agent doesn't); reuse the broker's
-  `recent_for` query. Last-turn timing + dashboard back-link
-  already shipped.
 - **State badge: compacting + napping states.** Idle/thinking already
   ship (driven from SSE turn_start/turn_end). Add `compacting 📦` and
   `napping 😴` once the `/compact` trigger and `nap` tool exist —