Keep a replay from moving the mesh backwards, and tighten the queue's edges (review of hq ADR 0219)

A registered replay asked now outranked newer asks of its module, and a plan
took any later outcome as its answer. A replay is now refused while the module
is asked anywhere, a plan module asked under an id is answered by that id
alone, and a rebuild of a commit asks what the module follows. An ask handed
back after a restart no longer reads as dead; a cancel that meets a start is
withdrawn; pause holds for an ask fetched as it lands; kill removes containers
before and after the build ends and says whether its outcome went out; a
holder may say only its own machine is paused.

cmd/mesh-controller/plan_retry.go

@@ -50,10 +50,20 @@ func pausedWaiting(p inventory.Plan, pause pauseView, now time.Time) (string, bo
 	if asked == nil {
 		return "", false
 	}
-	return fmt.Sprintf("waiting: the build seat is paused on %s (asked %s ago)",
-		strings.Join(pause.Nodes, ", "), now.Sub(*asked).Round(time.Second)), true
+	waited := now.Sub(*asked)
+	said := fmt.Sprintf("waiting: the build seat is paused on %s (asked %s ago)",
+		strings.Join(pause.Nodes, ", "), waited.Round(time.Second))
+	// Not late — a pause is a decision — but a pause forgotten is a plan that never moves, so one held
+	// longer than a day is named.
+	if waited > pausedTooLong {
+		said += " — PAUSED OVER A DAY: `resume` takes builds again"
+	}
+	return said, true
 }
 
+// pausedTooLong is how long a plan may wait on a paused build seat before it says the pause is long.
+const pausedTooLong = 24 * time.Hour
+
 // awaitsABuild is whether any open plan has an ask outstanding in its current tier — the only case
 // where the seat being paused changes what a plan says.
 func awaitsABuild(plans []inventory.Plan) bool {