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-sh4re/src/lib.rs

@@ -297,6 +297,11 @@ pub enum LooseEnd {
     UnreadMatrix {
         /// Number of rooms with at least one unread notification.
         rooms: u32,
+        /// Per-room summary: one line per room with truncated last-message
+        /// body when count is 1, or just the unread count otherwise. Empty
+        /// when the daemon returned no per-room detail.
+        #[serde(default)]
+        summary: String,
     },
 }
 
@@ -923,9 +928,7 @@ impl ToolGroup {
                 "get_logs — read a sub-agent container's systemd journal (privileged)"
             }
             Self::Execution => "bash_run, bash_status — run shell commands in the container",
-            Self::WebTools => {
-                "WebFetch, WebSearch — Claude built-in web egress; not MCP tools"
-            }
+            Self::WebTools => "WebFetch, WebSearch — Claude built-in web egress; not MCP tools",
         }
     }
 }