Say a read-only mesh-cli call in no line of its own, and count them hourly (hq issue 762)

A page polling plans every few seconds wrote about 14,000 journal lines a day. A line is judged a
read by the generic command verb's reading forms (ADR 0266), on its every word, so plans go,
conditions silence and settings set are still said; a refused or failed read is said too.

cmd/mesh-controller/sayable_test.go

@@ -43,6 +43,9 @@ func TestMain(m *testing.M) {
 	}
 	if os.Getenv(echoEnvironment) != "" {
 		fmt.Printf("verb=%q caller=%q terminal=%v\n", os.Getenv("MESH_VERB"), os.Getenv("MESH_CALLER"), startedAtTheTerminal())
+		if os.Getenv(echoFails) != "" {
+			os.Exit(3)
+		}
 		os.Exit(0)
 	}
 	conditions.Unsayable = func(o conditions.Observation, field string, r outward.Refusal) {