fix(latest,web): finish the atomic deletion and honest empty states (#145)

Review fixes on top of cb2b104:
- Delete the write-only in-memory refuseUntil map and setRefusalBackoff now
  that status.go is gone: the pass gate reads the durable stamp, so the map
  was half-deleted dead state (spec review C-1).
- An outcome-query failure no longer blanks the Lane table into the false
  'no data yet': rows render with 'none observed' chips instead (I-1).
- due-query and eligible-count skips get their own sentences instead of the
  merged 'check failed' (I-2).
- ADR-0012 constrain wording corrected and trailing newline added (M-1)

backend/internal/web/admin_lanes.go

@@ -84,13 +84,14 @@ func (h *Handler) lanesView() lanesView {
 		return v
 	}
 	now := time.Now()
-	outcomes, err := h.store.LanePassOutcomes(time.Now().Add(-ownerWindow).UnixMilli())
+	outcomes, err := h.store.LanePassOutcomes(now.Add(-ownerWindow).UnixMilli())
 	if err != nil {
+		// The rows are complete without the chips, so a failed outcome sum
+		// must not blank the table into "no data yet" — that is the confident
+		// wrong statement the page exists to avoid. Every row renders "none
+		// observed" instead, which is honest.
 		log.Printf("admin lanes: outcomes: %v", err)
-		return lanesView{
-			PollerOff:         v.PollerOff,
-			BrowserConfigured: v.BrowserConfigured,
-		}
+		outcomes = nil
 	}
 	bySite := make(map[string]store.SiteOutcomes, len(outcomes))
 	for _, o := range outcomes {
@@ -193,8 +194,11 @@ func laneState(p store.LanePass, now time.Time) (phrase string, good, attention
 	case latest.SkipAsleep:
 		phrase = "browser asleep"
 		good = true
-	case latest.SkipDueQuery, latest.SkipEligibleCount:
-		phrase = "check failed"
+	case latest.SkipDueQuery:
+		phrase = "due query failed"
+		attention = true
+	case latest.SkipEligibleCount:
+		phrase = "eligible count failed"
 		attention = true
 	case latest.SkipNothingEligible:
 		phrase = "nothing eligible"