Show each farm's gateway status and what discovery found

When the fleet page is empty or a printer is "unknown", the reason is
almost always upstream: the gateway is not connected, or discovery never
reported. A strip per farm now says which - "Gateway online/offline/
checking" (no answer yet is not offline) - with a collapsible list of the
printers discovery found, each marked already added, same address as an
added printer, or not added yet, using the backend's serial/address match.
It also says plainly when discovery has not reported at all, which is the
default, as distinct from a scan that found nothing.

Read-only on purpose: adding a printer from the UI still needs the proxy's
offline-capable store and a credential pass-through that is never kept in
the cloud. Polled every 10s (gateway presence has no push channel); a
failed poll keeps the last answer instead of flipping to offline.

Checked in real Chrome against the live stack (Gateway online, discovery
not reported, no page errors); the static SPA still generates, now 6 routes.

packages/ui/src/components/FarmStatus.vue

@@ -0,0 +1,75 @@
+<script setup lang="ts">
+import { computed } from "vue";
+import type { AppFarm, AppFarmDiscovery } from "../types";
+
+const props = defineProps<{ farm: AppFarm; status: AppFarmDiscovery | null }>();
+
+// Three honest answers, not two: no answer yet is not "offline".
+const gateway = computed(() =>
+  props.status === null ? "checking" : props.status.gatewayOnline ? "online" : "offline",
+);
+
+const candidates = computed(() => props.status?.discovery?.printers ?? []);
+
+const discoveryNote = computed(() => {
+  if (!props.status) return "";
+  if (props.status.discovery === null)
+    return "Discovery has not reported - it is off by default on a gateway.";
+  if (!candidates.value.length)
+    return `Scanned ${new Date(props.status.discovery.scannedAt).toLocaleString()}: nothing found.`;
+  return `Scanned ${new Date(props.status.discovery.scannedAt).toLocaleString()}.`;
+});
+
+const label = (c: { name?: string | null; model?: string | null; vendor: string }) =>
+  [c.name, c.model].filter(Boolean).join(" / ") || c.vendor;
+</script>
+
+<template>
+  <section class="farm-status" :aria-label="`Farm ${farm.name}`">
+    <span class="farm-status__name">{{ farm.name }}</span>
+    <span class="farm-status__gateway" :class="`is-${gateway}`">Gateway {{ gateway }}</span>
+    <details v-if="status" class="farm-status__discovery">
+      <summary>Discovered printers ({{ candidates.length }})</summary>
+      <p>{{ discoveryNote }}</p>
+      <ul v-if="candidates.length">
+        <li v-for="c in candidates" :key="c.address + (c.serial ?? '')">
+          <strong>{{ label(c) }}</strong> - {{ c.vendor }} at {{ c.address }}
+          <template v-if="c.matchedOn === 'serial'"> - already added</template>
+          <template v-else-if="c.matchedOn === 'address'"> - same address as an added printer (check)</template>
+          <template v-else> - not added yet</template>
+        </li>
+      </ul>
+    </details>
+  </section>
+</template>
+
+<style scoped>
+.farm-status {
+  display: flex;
+  gap: 1rem;
+  align-items: baseline;
+  flex-wrap: wrap;
+  font-size: 0.9rem;
+}
+
+.farm-status__name {
+  font-weight: 600;
+}
+
+.farm-status__gateway.is-online {
+  color: #35d07f;
+}
+
+.farm-status__gateway.is-offline {
+  color: #f2604c;
+}
+
+.farm-status__gateway.is-checking {
+  opacity: 0.6;
+}
+
+.farm-status__discovery ul {
+  margin: 0.25rem 0 0;
+  padding-left: 1.25rem;
+}
+</style>

packages/ui/src/index.ts

@@ -4,4 +4,5 @@ export { default as TemperatureGraph } from "./components/TemperatureGraph.vue";
 export { default as WebRTCStreamView } from "./components/WebRTCStreamView.vue";
 export { default as JobList } from "./components/JobList.vue";
 export { default as JobUpload } from "./components/JobUpload.vue";
-export type { AppFarm, AppJob, AppPrinterState, AppTelemetryMessage, PrinterCommand } from "./types";
+export { default as FarmStatus } from "./components/FarmStatus.vue";
+export type { AppDiscoveredCandidate, AppFarm, AppFarmDiscovery, AppJob, AppPrinterState, AppTelemetryMessage, PrinterCommand } from "./types";

packages/ui/src/types.ts

@@ -79,3 +79,25 @@ export interface AppJob {
   progressPct?: number | null;
   createdAt: string;
 }
+
+/**
+ * `GET /farms/:id/discovered-printers`. `discovery` is null when the gateway
+ * has never reported a scan - almost always because discovery is off, which
+ * is its default - and that is not the same as a report with no printers.
+ */
+export interface AppDiscoveredCandidate {
+  address: string;
+  vendor: string;
+  name?: string | null;
+  model?: string | null;
+  serial?: string | null;
+  /** The printer row this candidate looks like, and how sure that is. */
+  existingPrinterId?: string | null;
+  matchedOn?: "serial" | "address" | null;
+}
+
+export interface AppFarmDiscovery {
+  farmId: string;
+  gatewayOnline: boolean;
+  discovery: { scannedAt: string; printers: AppDiscoveredCandidate[] } | null;
+}