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/tool_groups.rs

@@ -72,8 +72,10 @@ fn write(map: &BTreeMap<String, Vec<String>>) -> std::io::Result<()> {
 /// Returns `Ok(())` when all names are known, or `Err` listing the
 /// unrecognised names so callers can surface a useful error message.
 pub fn validate_groups(groups: &[String]) -> anyhow::Result<()> {
-    let valid: std::collections::BTreeSet<&str> =
-        hive_sh4re::ToolGroup::ALL.iter().map(|g| g.as_str()).collect();
+    let valid: std::collections::BTreeSet<&str> = hive_sh4re::ToolGroup::ALL
+        .iter()
+        .map(|g| g.as_str())
+        .collect();
     let unknown: Vec<&str> = groups
         .iter()
         .map(String::as_str)