Hold a plan whose backup failed or stayed silent, say it, and ask again by a verb (issue 1066)

cmd/mesh-controller/doctor.go

@@ -174,6 +174,10 @@ var probeRegistry = []probe{
 	{ID: busStepProbe, Asserts: "a bus upgrade a person started is said while it runs, and is followed by the bus's " +
 		"health within its bound — or is said failed, with its snapshot as the way back", From: "ADR 0236, to-be 45 §8",
 		Kind: kindBusMaintenance, Raises: []string{kindBusUpgradeFailed}, Phase: 4, run: probeBusStep},
+	// A delivery plan held for a backup that failed or stayed silent (ADR 0404 decision 4): one condition per plan.
+	{ID: backupHeldProbe, Asserts: "no delivery plan is held for a backup before its send that failed or did not " +
+		"answer in ten minutes", From: "ADR 0404 decision 4, issue 1066", Kind: kindBackupHeld, Phase: 1,
+		run: probeBackupHeld},
 }
 
 // probeVerdict is one probe's outcome in a run.