feat(#1137): rich unread summary in loose ends and wake signal

- hive-sh4re: UnreadMatrix gains summary: String field (per-room breakdown)
- hive-matrix-mcp/protocol: add RoomUnread struct + UnreadSummary request
- hive-matrix-mcp/handlers: collect_unread() fetches per-room data;
  single-unread rooms include truncated last-message body + sender;
  multi-unread rooms carry count only
- hive-matrix-mcp/wake: format_unread_summary() builds wake body from
  RoomUnread slice; terse one-liner for single-room/single-message,
  bulleted list for multi-room; always appends read-hint
- hive-matrix-mcp/timeline: wake body now covers all rooms with unread
  at fire time, not just the triggering event; falls back to per-event
  teaser if notification counts haven't updated yet
- hive-ag3nt/mcp: matrix_unread_summary() replaces matrix_unread_rooms();
  UnreadMatrix loose end carries per-room summary lines; render shows
  room breakdown with sender: body for single-unread rooms

hive-c0re/src/manager_server.rs

@@ -299,9 +299,14 @@ async fn dispatch(req: &ManagerRequest, coord: &Arc<Coordinator>) -> ManagerResp
             let result = match agent.as_deref() {
                 Some("*") => {
                     // Hive-wide query requires query_agent_state capability.
-                    if !crate::capabilities::has_cap(MANAGER_AGENT, hive_sh4re::Capability::QueryAgentState) {
+                    if !crate::capabilities::has_cap(
+                        MANAGER_AGENT,
+                        hive_sh4re::Capability::QueryAgentState,
+                    ) {
                         return ManagerResponse::Err {
-                            message: "query_agent_state capability required for hive-wide loose ends".into(),
+                            message:
+                                "query_agent_state capability required for hive-wide loose ends"
+                                    .into(),
                         };
                     }
                     crate::loose_ends::hive_wide(coord)