Spec #137: per-Series poll failure state, completion hint, and outbound owner notification (#174)

Implements spec #137 (spec 4 of 4 from wayfinder map #114).

Closes #137.

Tickets: #164, #165, #166, #167, #168, #169, #170, #171, #172, #173 — all closed, landed on this branch.

## Summary
- #164/#168: sixth outcome word `not_found`; per-Site completed marker predicate.
- #165/#169: `poll_failures` row is the failure state; the pass remembers a Site-reported completion.
- #166/#171: two new admin filters (`failing`, `unverified`); outbound owner notification + stall condition.
- #167/#170: a failure names itself on the Series page; the completion hint reaches the owner and decides nothing.
- #172: the other three fault conditions (no-browser-route, sidecar-down, adapter-broken) feeding the notifier.
- #173: the landing verdict line shares the same `latest.FaultsFrom` judgement the notifier uses, so the page and the push cannot disagree.

`cd backend && go test ./...` green on the merged branch (8 packages).

Reviewed-on: #174
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/internal/web/admin_lanes.go

@@ -56,6 +56,10 @@ type laneRow struct {
 	// offer Resume from the moment the owner presses Pause, with no pass
 	// having run to record it (issue #147).
 	Paused bool
+	// FailingHref is the one navigation the row offers: the Site's name
+	// links to that Site's failing Series. The chips beside it stay
+	// unlinked; the withdrawn promise lives on outcomeChips (issue #167).
+	FailingHref string
 }
 
 // chip is one named outcome count over the owner's window.
@@ -223,6 +227,7 @@ func buildLaneRow(p store.LanePass, o store.SiteOutcomes, now time.Time) laneRow
 	if p.GapMS > 0 {
 		row.Gap = (time.Duration(p.GapMS) * time.Millisecond).Truncate(time.Second).String()
 	}
+	row.FailingHref = seriesListHref(store.SeriesFilterFailing, p.Site, "", 0)
 	row.Chips = outcomeChips(o)
 	row.HasChips = len(row.Chips) > 0
 	row.StatePhrase, row.StateGood, row.Attention = laneState(p, now)
@@ -232,17 +237,24 @@ func buildLaneRow(p store.LanePass, o store.SiteOutcomes, now time.Time) laneRow
 
 // outcomeChips lists a Site's nonzero window sums in the taxonomy's fixed
 // order, so the chips never reorder as the window changes. None observed is
-// written by the template, not drawn as a confident zero count.
+// written by the template, not drawn as a confident zero count. The names are
+// spelled through outcomeWord, the one vocabulary the failure surface shares
+// with the Series list's fact line (issue #167). The counts stay unlinked
+// permanently — a withdrawn promise: two of the six words write no per-Series
+// state, and the other four count attempts inside the owner window while the
+// failing filter lists Series failing now, so neither set contains the other
+// and no chip can be a door to its list.
 func outcomeChips(o store.SiteOutcomes) []chip {
 	fixed := []struct {
 		name  string
 		count int
 	}{
-		{"refused", o.Refused},
-		{"unreachable", o.Unreachable},
-		{"no chapter", o.NoChapter},
-		{"unfetchable", o.Unfetchable},
-		{"errors", o.Errors},
+		{outcomeWord("refused"), o.Refused},
+		{outcomeWord("unreachable"), o.Unreachable},
+		{outcomeWord("no_chapter"), o.NoChapter},
+		{outcomeWord("unfetchable"), o.Unfetchable},
+		{outcomeWord("not_found"), o.NotFound},
+		{outcomeWord("errors"), o.Errors},
 	}
 	var out []chip
 	for _, f := range fixed {