mesh-knowledge: keep when an owed review is due, say it in the history, and tell the operator once after its last try (hq issue 497)

A failed review's try count was already kept with the version, but not when it was asked again, so a 10-minute
pause read as a review lost to a restart; and after the last try only the history and the health said so.

modules/mesh-knowledge/README.md

@@ -104,8 +104,11 @@ as text. `get` serves each, and any other field a record of hq wrote under `fiel
      Its author revises it by proposing it again, and that version is reviewed again.
    - A judgement that cannot be had (the judge unreachable, or an answer that is not `approve`, or `changes` naming
      no finding) leaves the record proposed and says so on it (`get`'s `review`). It is never taken as an
-     approval. It is asked again after 10, then 20 minutes; after 3 tries the record says its author proposes it
-     again to have it reviewed again, and the module is unhealthy, naming it, so the mesh raises a condition.
+     approval. It is owed: its try count and when it is asked again (10, then 20 minutes later) are kept with the
+     version in the store and said in its history, so the background work takes it up at that time, also after a
+     restart of the tool runner (hq issue 497). After 3 tries the record says it was the last and its author
+     proposes it again to have it reviewed again; the operator is told once on the operator's channel, and the
+     module is unhealthy, naming it, so the mesh raises a condition.
      An ask of the operator that cannot be made counts as a try the same way.
    - A review whose outcome the database refused to keep is held back for that record alone (10, then 20
      minutes, 3 tries, logged as given up), so it never blocks the records behind it.