Bug bash 5: the URL, the fleet loop, and an empty card

A link to a hub page no longer reloads onto the last machine; a link from a hub-only page to
a machine's page arrives at that page; a page being left no longer asks about the next page's
selection; the hub holds its machines to the rate it is itself running.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/api/server.go

@@ -1986,21 +1986,13 @@ func (s *Server) keepFleetInStep() {
 		} else {
 			time.Sleep(2 * time.Minute)
 		}
-		var ui struct {
-			RefreshMs float64 `json:"refreshMs"`
-		}
-		var histSec int
-		s.store.View(func(st *store.State) { _ = json.Unmarshal(st.UI, &ui); histSec = st.HistorySec })
-		want := map[string][2]any{} // path → {field, value}
-		if ui.RefreshMs >= 100 {
-			ms := int(ui.RefreshMs)
-			if hi := int(metrics.MaxInterval.Milliseconds()); ms > hi {
-				ms = hi
-			}
-			want["/api/prefs/sampler"] = [2]any{"ms", ms}
-		}
-		if histSec > 0 {
-			want["/api/prefs/history"] = [2]any{"seconds", histSec}
+		// What the hub itself is running is the fleet's answer — not what happens to be written
+		// in the UI prefs, which are only written when somebody changes a setting. A hub nobody
+		// has been into Settings on still has a sampling rate and a window, and its machines
+		// should be on them.
+		want := map[string][2]any{ // path → {field, value}
+			"/api/prefs/sampler": {"ms", int(s.metrics.Interval().Milliseconds())},
+			"/api/prefs/history": {"seconds", int(s.metrics.Window().Seconds())},
 		}
 		hdr := http.Header{"X-Hamlab-From-Hub": []string{"1"}, "Content-Type": []string{"application/json"}}
 		for _, name := range s.nodes.Names() {