Keep the controller lease through a renewal the bus did not answer, until its TTL passes

A bus stall of a few seconds made a renewal time out, and the controller
called that a lost lease, exited and raised the urgent lease-lost alert,
though no other controller could take a key that still lived. Now only
another holder seen, or the key's TTL passed unrenewed, loses the lease;
new acts stop at half the TTL unrenewed and resume on the next renewal
(novox/hq issue 477).

cmd/mesh-controller/acting.go

@@ -26,8 +26,11 @@ import (
 //
 //   - **The serving controller** takes it before it does anything else — before it asserts the bus's
 //     objects, which are the controller's to write — waiting while another holds it, and renews it.
-//     A renewal refused or failed is the lease lost: the gate closes at once and the process exits, so
-//     its service manager restarts it as a candidate (serve, in push.go).
+//     Another holder seen, or the key's age passed with no renewal made, is the lease lost: the gate
+//     closes at once and the process exits, so its service manager restarts it as a candidate (serve,
+//     in push.go). A renewal the bus does not answer in time is not a loss (novox/hq issue 477): the
+//     lease is kept, no new act starts once half the key's age passed unrenewed, and the next renewal
+//     made opens the gate again.
 //   - **A command run at a shell** — `push` in the installer, the lab, a person repairing a mesh whose
 //     controller is down (issue 201) — acts **under the holder's epoch** when a controller holds the
 //     lease: it is the same mesh's word, composed and sent under the store's hold of each machine like

cmd/mesh-controller/signals.go

@@ -862,7 +862,7 @@ func watchLease(f *signalFacts) []conditions.Observation {
 		}
 	}
 	if len(lost) > 0 {
-		how := "lost it: its renewal was refused or could not be made"
+		how := "lost it: another holder wrote its key, or no renewal was made within the key's age"
 		if newest.How == inventory.EpochExpired {
 			how = "stopped renewing it without giving it back, and was taken over"
 		}