review: verdigris patina, honest Lane figures, tests that can fail (#102)

Two-axis review found the shipped colour and three weak tests.

- --patina was a warm gold at the same hue family as --brass; the spec
  asked for a cool blue-green so an unhealthy Lane is unmistakably not
  ember. Now verdigris in both branches, with docs/design-system.md
  stating why the far side of the wheel is the point.
- A Lane pass that returns before computing its figures carries the
  previous pass's due count and gap forward instead of recording zeroes,
  and Checked rides beside Due so a stopped Lane is distinguishable from
  a quiet one.
- TestAdminPageWithoutAPollerSaysSo now separates the two causes it
  conflated, TestOwnerClearsReaderMarks seeds real counters so the
  clearing assertion can fail, and TestLaneStatus asserts Checked and
  the carry-forward.
- backend/AGENTS.md records the one deliberate owner comparison outside
  requireOwner and the carry-forward rule.

backend/internal/web/admin.go

@@ -31,7 +31,11 @@ type adminView struct {
 // browser fact, which is shared by the three browser Sites rather than held
 // once per Site.
 type lanesView struct {
-	Rows              []laneRow
+	Rows []laneRow
+	// PollerOff means no poller is running at all (disabled by config, or its
+	// client could not be built). The browser line must not answer "not
+	// configured" then: the sidecar is not the reason nothing is polled.
+	PollerOff         bool
 	BrowserConfigured bool
 	BrowserReachable  bool
 }
@@ -40,9 +44,15 @@ type lanesView struct {
 // template renders strings and flags, and every judgement about what they mean
 // is made here.
 type laneRow struct {
-	Site     string
-	Due      int
-	Ran      string
+	Site string
+	Due  int
+	Ran  string
+	// Checked is how many Series the last pass read. Due without Checked is a
+	// Lane that has stopped working; the two figures side by side are what
+	// separate that from a Lane with nothing to do.
+	Checked int
+	// Gap is empty when no pass has reached the pace yet, so the row omits the
+	// figure instead of stating a zero.
 	Gap      string
 	Clamped  bool
 	Refusing bool
@@ -50,6 +60,9 @@ type laneRow struct {
 	// sidecar while the sidecar is unreachable — including the case where none
 	// is configured, which stops those Series just as completely.
 	BrowserLost bool
+	// Stalled marks a Lane with Series waiting that its last pass did not read
+	// — the difference between a stopped Lane and a quiet one (story 13).
+	Stalled bool
 	// Attention is the one flag the template colours on, so an unhealthy Lane
 	// is found at a glance rather than read for.
 	Attention bool
@@ -127,7 +140,7 @@ func (h *Handler) uiLanes(w http.ResponseWriter, r *http.Request) {
 // — an empty page a few seconds after a restart must not read as a stopped one.
 func (h *Handler) lanesView() lanesView {
 	if h.lanes == nil {
-		return lanesView{}
+		return lanesView{PollerOff: true}
 	}
 	snap := h.lanes.LaneStatus()
 	v := lanesView{
@@ -138,15 +151,24 @@ func (h *Handler) lanesView() lanesView {
 	now := time.Now()
 	for _, l := range snap.Lanes {
 		lost := l.Browser && !snap.BrowserReachable
+		// Series waiting and none read is the shape of a Lane that has stopped
+		// working, as distinct from one that is quiet for want of work.
+		stalled := l.Due > 0 && l.Checked == 0
+		gap := ""
+		if l.Gap > 0 {
+			gap = l.Gap.Truncate(time.Second).String()
+		}
 		v.Rows = append(v.Rows, laneRow{
 			Site:        l.Site,
 			Due:         l.Due,
 			Ran:         since(now, l.LastRun),
-			Gap:         l.Gap.Truncate(time.Second).String(),
+			Checked:     l.Checked,
+			Gap:         gap,
 			Clamped:     l.Clamped,
 			Refusing:    l.Refusing,
 			BrowserLost: lost,
-			Attention:   l.Clamped || l.Refusing || lost,
+			Stalled:     stalled,
+			Attention:   l.Clamped || l.Refusing || lost || stalled,
 		})
 	}
 	return v