Panel 3 — live per-node metrics. One row per node from the latest collector
frame: a throughput sparkline + rate, a visual p50/p95 latency bar, completed
count, and error rate, with a state pill. A totals row sums the network. The
frame arrives on a 1 Hz PubSub tick handled by Bloccs.Web.DashboardLive; idle
nodes show "—" until traffic flows.