harness todos: ack reconciled todos instead of deleting them

hive-agent/src/disk_watch.rs

@@ -15,7 +15,10 @@
 //! loose-ends list instead of waking the agent every tick. Only crossing
 //! into a new bucket (or a change in which directories are big enough to
 //! list) speaks up again. Dropping back under the threshold clears the
-//! todo.
+//! todo. Acknowledging the todo (`cancel_loose_end`) does not defeat this —
+//! `Todos::mark_done` acks the row rather than deleting it, so the next
+//! probe still has the prior summary to compare against instead of seeing
+//! an empty table and re-announcing an unchanged condition as new.
 //!
 //! Scoped by design: the `statvfs` reads the *whole filesystem*, which on
 //! a shared host volume (several agents' state dirs on the same