Count a plan's time from its tier, and save it only when a step changed it (hq issue 296)

plans said a build queued for minutes had been building for a few seconds: the line counted from
the last save, and every advance saved the plan whether or not it moved, bumping its revision and
saying plan-moved on the bus. The line, status and LATE now count from when the plan entered its
tier with the stalled condition's bound, and an advance that changes nothing writes nothing.

cmd/mesh-controller/status.go

@@ -143,14 +143,14 @@ func printStatus(asked answers) error {
 			len(quiet), strings.Join(said, "\n  "))
 	}
 
-	if open, late := openPlans(asked.plans, asked.paused); len(open) > 0 {
+	if open, late := openPlans(asked.plans, time.Now(), asked.paused, asked.tierBounds); len(open) > 0 {
 		fmt.Printf("%d plan(s) open", len(open))
 		if late > 0 {
-			fmt.Printf(", %d waiting past %s", late, planWaitBound)
+			fmt.Printf(", %d in a tier past its bound", late)
 		}
 		fmt.Println(":")
 		for _, p := range open {
-			fmt.Printf("  %s\n", planLineWith(p, time.Now(), asked.paused))
+			fmt.Printf("  %s\n", planLineWith(p, time.Now(), asked.paused, asked.tierBounds.of(p.Repository)))
 		}
 		fmt.Println()
 	}
@@ -472,6 +472,8 @@ func theThreeQuestions(ctx context.Context, open *stores) (answers, error) {
 	}
 	// Whether the build seat takes work, for a plan waiting on it (novox/hq ADR 0219).
 	out.paused = buildSeatPause(ctx, inv, out.plans)
+	// And how long a tier may take, the bound a plan is late at (novox/hq issue 296).
+	out.tierBounds = readTierBounds(ctx, inv, time.Now())
 	// And how many repairs were done by hand this week (novox/hq to-be 45 §7) — where there is a bus
 	// to read the log from; a process with none has no log to count.
 	if _, onBus := broker.BusAddress(); onBus == nil {