feat(ui): Federation adopts the cached-resource store (B4)

federation nodes + dwn.status become useCachedResource entries: revisits
paint the node list instantly, `loading` fires on true first-load only
(the old showLoader semantics), the 5s poll refreshes silently like the
old surfaceErrors:false path, and explicit reloads after mutations still
surface failures in the error banner. Replaces the hand-rolled
loadNodesWithOptions SWR.

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

neode-ui/src/views/Federation.vue

@@ -229,6 +229,7 @@
 <script setup lang="ts">
 import { ref, computed, onMounted, onUnmounted } from 'vue'
 import { rpcClient } from '@/api/rpc-client'
+import { useCachedResource } from '@/composables/useCachedResource'
 import { useTransportStore } from '@/stores/transport'
 import { useAppStore } from '@/stores/app'
 import { useSyncStore } from '@/stores/sync'
@@ -250,8 +251,15 @@ const transportStore = useTransportStore()
 const appStore = useAppStore()
 const syncStore = useSyncStore()
 
-const nodes = ref<FederatedNode[]>([])
-const loading = ref(true)
+// Cached: revisits paint the node list instantly; the 5s poll and mutation
+// refreshes revalidate behind it. `loading` is initial-load only (background
+// refreshes keep content on screen — the old showLoader:false semantics).
+const nodesRes = useCachedResource<FederatedNode[]>({
+  key: 'federation.nodes',
+  fetcher: async () => (await rpcClient.federationListNodes()).nodes,
+})
+const nodes = computed(() => nodesRes.data.value ?? [])
+const loading = computed(() => nodesRes.loadState.value === 'loading')
 const error = ref('')
 const selectedNode = ref<FederatedNode | null>(null)
 const inviteType = ref<'trusted' | 'observer'>('trusted')
@@ -320,7 +328,12 @@ const mapLinks = computed(() => {
   }))
 })
 
-const dwnStatus = ref<DwnStatus | null>(null)
+const dwnStatusRes = useCachedResource<DwnStatus>({
+  key: 'federation.dwn-status',
+  fetcher: (signal) => rpcClient.call<DwnStatus>({ method: 'dwn.status', signal, dedup: true, maxRetries: 1 }),
+  immediate: false,
+})
+const dwnStatus = computed(() => dwnStatusRes.data.value)
 const dwnSyncing = ref(false)
 
 const dwnSyncDotClass = computed(() => {
@@ -500,25 +513,13 @@ function isOnlineCheck(node: FederatedNode): boolean {
   return lastSeen > tenMinutesAgo
 }
 
+/** Explicit reload (mutations, retry): surfaces a load failure in the error
+ *  banner. The background poll calls nodesRes.refresh() directly and stays
+ *  silent, like the old surfaceErrors:false path. */
 async function loadNodes() {
-  return loadNodesWithOptions()
-}
-
-async function loadNodesWithOptions(options: { showLoader?: boolean; surfaceErrors?: boolean } = {}) {
-  const showLoader = options.showLoader ?? nodes.value.length === 0
-  const surfaceErrors = options.surfaceErrors ?? true
-  try {
-    if (showLoader) loading.value = true
-    const result = await rpcClient.federationListNodes()
-    nodes.value = result.nodes
-    error.value = ''
-  } catch (e) {
-    if (surfaceErrors) {
-      error.value = e instanceof Error ? e.message : 'Failed to load nodes'
-    }
-  } finally {
-    if (showLoader) loading.value = false
-  }
+  await nodesRes.refresh()
+  if (nodesRes.error.value) error.value = nodesRes.error.value
+  else error.value = ''
 }
 
 function handleGenerateInvite(type: 'trusted' | 'observer') {
@@ -610,13 +611,8 @@ async function deployApp(did: string, appId: string) {
   }
 }
 
-async function loadDwnStatus() {
-  try {
-    const result = await rpcClient.call<DwnStatus>({ method: 'dwn.status' })
-    dwnStatus.value = result
-  } catch {
-    dwnStatus.value = null
-  }
+function loadDwnStatus() {
+  return dwnStatusRes.refresh()
 }
 
 async function triggerDwnSync() {
@@ -681,7 +677,6 @@ async function rotateDid(password: string) {
 let autoRefreshTimer: ReturnType<typeof setInterval> | null = null
 
 onMounted(async () => {
-  loadNodesWithOptions({ showLoader: true })
   loadDwnStatus()
   loadDiscoveryState()
   loadPendingRequests()
@@ -694,7 +689,7 @@ onMounted(async () => {
     // Self DID not available
   }
   autoRefreshTimer = setInterval(() => {
-    loadNodesWithOptions({ showLoader: false, surfaceErrors: false })
+    void nodesRes.refresh()
     loadPendingRequests()
   }, 5000)
 })