export an open-todos gauge and chart it on the agent dashboard

hive-agent/src/todos.rs

@@ -376,6 +376,24 @@ impl Todos {
         Ok(any)
     }
 
+    /// Number of un-acked todo rows across every subsystem: the length of
+    /// [`Todos::list`]`(None)`, without materialising the rows.
+    ///
+    /// # Errors
+    ///
+    /// Propagates the sqlite query failure.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the connection mutex is poisoned.
+    pub fn open_count(&self) -> Result<u64> {
+        let conn = self.conn.lock().unwrap();
+        let n: u64 = conn.query_row("SELECT COUNT(*) FROM todos WHERE acked = 0", [], |row| {
+            row.get(0)
+        })?;
+        Ok(n)
+    }
+
     /// Reap acked rows whose `acked_at` is older than `cutoff` (a unix
     /// timestamp). Called by the harness's hourly vacuum sweep
     /// (`vacuum.rs`), not on any hot path — bounds the table against acked
@@ -492,6 +510,21 @@ mod tests {
         );
     }
 
+    #[test]
+    fn open_count_follows_adds_and_acks() {
+        let (_dir, s) = store();
+        assert_eq!(s.open_count().unwrap(), 0);
+        let (a, _) = s.upsert("bash", None, "one", None, false).unwrap();
+        s.upsert("bash", None, "two", None, false).unwrap();
+        s.upsert("matrix", Some("!r:x"), "three", None, false)
+            .unwrap();
+        assert_eq!(s.open_count().unwrap(), 3);
+        s.mark_done(a).unwrap();
+        assert_eq!(s.open_count().unwrap(), 2, "acked rows are not open");
+        assert_eq!(s.clear("matrix", Some("!r:x")).unwrap(), 1);
+        assert_eq!(s.open_count().unwrap(), 1);
+    }
+
     #[test]
     fn has_any_reflects_emptiness() {
         let (_dir, s) = store();