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/meta.rs

@@ -365,7 +365,10 @@ pub async fn commit_capabilities(agent: &str, caps: &[String]) -> Result<()> {
 /// logged as warnings and don't propagate: the topology write already
 /// succeeded, and `sync_agents` will pick up any un-committed change
 /// on the next run as a safety net.
-pub async fn commit_topology(child: &str, new_parent: Option<&str>) -> std::result::Result<(), String> {
+pub async fn commit_topology(
+    child: &str,
+    new_parent: Option<&str>,
+) -> std::result::Result<(), String> {
     let _guard = META_LOCK.lock().await;
     crate::topology::set_parent(child, new_parent)?;
     let dir = meta_dir();
@@ -374,11 +377,7 @@ pub async fn commit_topology(child: &str, new_parent: Option<&str>) -> std::resu
         if has_staged_changes(&dir).await? {
             git_commit(
                 &dir,
-                &format!(
-                    "topology: {} → {}",
-                    child,
-                    new_parent.unwrap_or("<root>")
-                ),
+                &format!("topology: {} → {}", child, new_parent.unwrap_or("<root>")),
             )
             .await?;
         }
@@ -526,7 +525,10 @@ where
         out.push_str("    nixpkgs-unstable.follows = \"hyperhive/nixpkgs-unstable\";\n");
     } else {
         let _ = writeln!(out, "    nixpkgs.url = \"{nixpkgs_flake}\";");
-        let _ = writeln!(out, "    nixpkgs-unstable.url = \"{nixpkgs_unstable_flake}\";");
+        let _ = writeln!(
+            out,
+            "    nixpkgs-unstable.url = \"{nixpkgs_unstable_flake}\";"
+        );
         let _ = writeln!(out, "    hyperhive.url = \"{hyperhive_flake}\";");
         out.push_str("    hyperhive.inputs.nixpkgs.follows = \"nixpkgs\";\n");
         out.push_str("    hyperhive.inputs.nixpkgs-unstable.follows = \"nixpkgs-unstable\";\n");